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<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2021-02-05T21:52:33.4416263+00:00 -->
<!-- Version            : 5.0.1.571 -->
<!-- Package ID         : c7364437af074432a4a571e2f16dd8a5 -->
<!-- Copyright (c) 2021 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="ajg_ContingentRevenueMember" name="ContingentRevenueMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_GainsOnDivestituresMember" name="GainsOnDivestituresMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_PremiumsPayableToUnderwritingEnterprises" name="PremiumsPayableToUnderwritingEnterprises" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_AccruedCompensationAndOtherAccruedLiabilities" name="AccruedCompensationAndOtherAccruedLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_PremiumFinancingBorrowings" name="PremiumFinancingBorrowings" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_AmortizationOfDeferredCompensationAndRestrictedStock" name="AmortizationOfDeferredCompensationAndRestrictedStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_IncreaseDecreaseInPremiumsAndFeeReceivable" name="IncreaseDecreaseInPremiumsAndFeeReceivable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_NetChangeInAccruedCompensationAndOtherAccruedLiabilities" name="NetChangeInAccruedCompensationAndOtherAccruedLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_PaymentsToAcquireBusinessesNetOfCashAndRestrictedCashAcquired" name="PaymentsToAcquireBusinessesNetOfCashAndRestrictedCashAcquired" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_NetProceedsFromSalesOfOperations" name="NetProceedsFromSalesOfOperations" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_EarnoutPaymentsForAcquisitions" name="EarnoutPaymentsForAcquisitions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_NetBorrowingsOnPremiumFinancingDebtFacility" name="NetBorrowingsOnPremiumFinancingDebtFacility" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_PaymentsForProceedsFromSettlementsOfTerminatedInterestRateSwaps" name="PaymentsForProceedsFromSettlementsOfTerminatedInterestRateSwaps" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_MinorityInterestIncreaseDecreaseFromRedemptions" name="MinorityInterestIncreaseDecreaseFromRedemptions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_DeferredCompensationAndRestrictedStockInShares" name="DeferredCompensationAndRestrictedStockInShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DeferredCompensationAndRestrictedStockExpensesBenefit" name="DeferredCompensationAndRestrictedStockExpensesBenefit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_OtherFinancialDataDisclosureTextBlock" name="OtherFinancialDataDisclosureTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_StockOptionPlansTextBlock" name="StockOptionPlansTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_RestrictedStockAndCashAwardsTextBlock" name="RestrictedStockAndCashAwardsTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_NatureOfOperationPolicyTextBlock" name="NatureOfOperationPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_RiskManagementSegmentPolicyTextBlock" name="RiskManagementSegmentPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PremiumsAndFeesReceivablePolicyTextBlock" name="PremiumsAndFeesReceivablePolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PremiumFinancingPolicyTextBlock" name="PremiumFinancingPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_RetentionBonusArrangementsPolicyPolicyTextBlock" name="RetentionBonusArrangementsPolicyPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ScheduleOfEstimatedUsefulLifeOfFixedAssetsTableTextBlock" name="ScheduleOfEstimatedUsefulLifeOfFixedAssetsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ScheduleOfBusinessAcquisitionAcquisitionOfAssetsTableTextBlock" name="ScheduleOfBusinessAcquisitionAcquisitionOfAssetsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ScheduleOfBusinessAcquisitionProFormaTableTextBlock" name="ScheduleOfBusinessAcquisitionProFormaTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ContractWithCustomerLiabilityTableTextBlock" name="ContractWithCustomerLiabilityTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_CarryingAmountOfGoodwillAllocatedByDomesticAndForeignOperationsTableTextBlock" name="CarryingAmountOfGoodwillAllocatedByDomesticAndForeignOperationsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ScheduleOfRestrictedStockAwardsVestingPeriodsTableTextBlock" name="ScheduleOfRestrictedStockAwardsVestingPeriodsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ScheduleOfChangesInPensionBenefitObligationsAndFairValueOfPlanAssetsTableTextBlock" name="ScheduleOfChangesInPensionBenefitObligationsAndFairValueOfPlanAssetsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ComponentsOfPeriodicPensionBenefitCostAndOtherChangesInPlanAssetsAndObligationsRecognizedInEarningsAndOtherComprehensiveEarningsTableTextBlock" name="ComponentsOfPeriodicPensionBenefitCostAndOtherChangesInPlanAssetsAndObligationsRecognizedInEarningsAndOtherComprehensiveEarningsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_SummaryOfPlansWeightedAverageAssetAllocationsTableTextBlock" name="SummaryOfPlansWeightedAverageAssetAllocationsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_OperatingLeasesCashFlowRelatedInformation" name="OperatingLeasesCashFlowRelatedInformation" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_OperatingLeaseRelatedAssetsAndLiabilitiesAndOtherRelatedInformation" name="OperatingLeaseRelatedAssetsAndLiabilitiesAndOtherRelatedInformation" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_SummaryOfNotionalAndFairValuesOfDerivativeInstrumentsTableTextBlock" name="SummaryOfNotionalAndFairValuesOfDerivativeInstrumentsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ScheduleOfOffBalanceSheetCommitmentsTableTextBlock" name="ScheduleOfOffBalanceSheetCommitmentsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ComponentsOfEarningsFromContinuingOperationsBeforeIncomeTaxesAndProvisionForIncomeTaxesTableTextBlock" name="ComponentsOfEarningsFromContinuingOperationsBeforeIncomeTaxesAndProvisionForIncomeTaxesTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_SignificantAccountingPoliciesLineItems" name="SignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_SignificantAccountingPoliciesTable" name="SignificantAccountingPoliciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ExpirationListsMember" name="ExpirationListsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_EmployeeStockPurchasePlanMember" name="EmployeeStockPurchasePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NumberOfCommercialCleanCoalProductionFacilities" name="NumberOfCommercialCleanCoalProductionFacilities" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_NumberOfCountriesInWhichCompanyHasOperations" name="NumberOfCountriesInWhichCompanyHasOperations" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_NumberOfCountriesInWhichCompanyDoesBusinessThroughNetworkOfCorrespondentBrokersAndConsultants" name="NumberOfCountriesInWhichCompanyDoesBusinessThroughNetworkOfCorrespondentBrokersAndConsultants" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DescriptionOfContractsRenewalPeriod" name="DescriptionOfContractsRenewalPeriod" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PercentageOfCommissionsAndFeeRevenuesRecognizedOnEffectiveDateOfInsuranceContract" name="PercentageOfCommissionsAndFeeRevenuesRecognizedOnEffectiveDateOfInsuranceContract" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PercentageOfCommissionsAndFeeRevenuesRecognizedInFirstThreeMonthsOfInsuranceContract" name="PercentageOfCommissionsAndFeeRevenuesRecognizedInFirstThreeMonthsOfInsuranceContract" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PercentageOfCommissionsAndFeeRevenuesRecognizedAfterFirstThreeMonthsOfInsuranceContract" name="PercentageOfCommissionsAndFeeRevenuesRecognizedAfterFirstThreeMonthsOfInsuranceContract" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_AllowancesForEstimatedPolicyCancellations" name="AllowancesForEstimatedPolicyCancellations" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_InsuranceContractsPremiumFinancingTerms" name="InsuranceContractsPremiumFinancingTerms" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_RegulatoryAssetsAbstract" name="RegulatoryAssetsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_RefinedFuelPlantsMember" name="RefinedFuelPlantsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateFairMarketValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateFairMarketValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RecordedEarnOutPayable" name="RecordedEarnOutPayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAccruedLiability" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAccruedLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_BusinessAcquisitionCostOfAcquiredEntityPurchasePriceNet" name="BusinessAcquisitionCostOfAcquiredEntityPurchasePriceNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_MaximumPotentialEarnoutPayable" name="MaximumPotentialEarnoutPayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_CapsicumReinsuranceBrokersLLPMember" name="CapsicumReinsuranceBrokersLLPMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_HanoverExcessAndSurplusIncAndHanoverPremiumFinanceIncMember" name="HanoverExcessAndSurplusIncAndHanoverPremiumFinanceIncMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CRESInsuranceServicesLLCMember" name="CRESInsuranceServicesLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_OptimumTalentIncMember" name="OptimumTalentIncMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AshtonTiffanyLLCMember" name="AshtonTiffanyLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CoolInsuringAgencyIncMember" name="CoolInsuringAgencyIncMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_HardsenAndAssociatesIncMember" name="HardsenAndAssociatesIncMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_OtherAcquisitionsMember" name="OtherAcquisitionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_BusinessAcquisitionNumberOfEmployeesInAcquiredCompany" name="BusinessAcquisitionNumberOfEmployeesInAcquiredCompany" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_BusinessAcquisitionNumberOfOperatingOfficesInAcquiredCompany" name="BusinessAcquisitionNumberOfOperatingOfficesInAcquiredCompany" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_TheBollingtonWilsonGroupMember" name="TheBollingtonWilsonGroupMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandTwentyAcquisitionsMember" name="TwoThousandTwentyAcquisitionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InsuranceBrokerageManagementServicesMember" name="InsuranceBrokerageManagementServicesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandTwentyAcquisitionMember" name="TwoThousandTwentyAcquisitionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandNineteenAcquisitionsMember" name="TwoThousandNineteenAcquisitionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InsuranceBrokerageAndRiskManagementServicesMember" name="InsuranceBrokerageAndRiskManagementServicesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_BusinessAcquisitionMember" name="BusinessAcquisitionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_BrokerageSegmentMember" name="BrokerageSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_BusinessCombinationAggregateEarnoutObligationMaximum" name="BusinessCombinationAggregateEarnoutObligationMaximum" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_BusinessCombinationAggregateEarnoutObligationRecordedMaximum" name="BusinessCombinationAggregateEarnoutObligationRecordedMaximum" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCash" name="BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCash" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCashOrStockAtOption" name="BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCashOrStockAtOption" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalentsAndRestrictedCash" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalentsAndRestrictedCash" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_BusinessAcquisitionsPurchasePriceAllocationGoodwillAmount" name="BusinessAcquisitionsPurchasePriceAllocationGoodwillAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ExpirationLists" name="ExpirationLists" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_BusinessAcquisitionActualRevenueAndPreTaxIncomeLossLineItems" name="BusinessAcquisitionActualRevenueAndPreTaxIncomeLossLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_BusinessAcquisitionActualRevenueAndPreTaxIncomeLossTable" name="BusinessAcquisitionActualRevenueAndPreTaxIncomeLossTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FairValueInputsAttritionRate" name="FairValueInputsAttritionRate" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_BusinessAcquisitionPurchasePriceAllocationGoodwillNotExpectedTaxDeductibleAmount" name="BusinessAcquisitionPurchasePriceAllocationGoodwillNotExpectedTaxDeductibleAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_BusinessAcquisitionsProFormaNetIncomeLossToControllingInterest" name="BusinessAcquisitionsProFormaNetIncomeLossToControllingInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_BusinessCombinationAnnualizeRevenue" name="BusinessCombinationAnnualizeRevenue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ContractWithCustomerLiabilityAdditions" name="ContractWithCustomerLiabilityAdditions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_NetChangeInCollectedBillingsAndDepositsReceivedFromCustomers" name="NetChangeInCollectedBillingsAndDepositsReceivedFromCustomers" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_ContractWithCustomerImpactOfChangeInForeignExchangeRates" name="ContractWithCustomerImpactOfChangeInForeignExchangeRates" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_RiskManagementSegmentMember" name="RiskManagementSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AccruedSupplementalDirectBillAndOtherReceivablesCurrent" name="AccruedSupplementalDirectBillAndOtherReceivablesCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RefinedCoalProductionRelatedReceivablesCurrent" name="RefinedCoalProductionRelatedReceivablesCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ComputerEquipmentGross" name="ComputerEquipmentGross" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_LandAndBuildingsGross" name="LandAndBuildingsGross" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_PropertyPlantAndEquipmentUsefulLifeAndValuesAbstract" name="PropertyPlantAndEquipmentUsefulLifeAndValuesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_OtherForeignMember" name="OtherForeignMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DebtLongTermAndShortTermCombinedAmountGross" name="DebtLongTermAndShortTermCombinedAmountGross" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_FixedRateOfThreePointFourEightPercentBalloonDueJuneTwentyFourTwoThousandTwentyMember" name="FixedRateOfThreePointFourEightPercentBalloonDueJuneTwentyFourTwoThousandTwentyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfThreePointNineNinePercentBalloonDueJulyTenTwoThousandTwentyMember" name="FixedRateOfThreePointNineNinePercentBalloonDueJulyTenTwoThousandTwentyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFivePointOneEightPercentBalloonDueFebruaryTenTwoThousandTwentyOneMember" name="FixedRateOfFivePointOneEightPercentBalloonDueFebruaryTenTwoThousandTwentyOneMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfThreePointSixNinePercentBalloonDueJuneFourteenTwoThousandTwentyTwoMember" name="FixedRateOfThreePointSixNinePercentBalloonDueJuneFourteenTwoThousandTwentyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFivePointFourNinePercentBalloonDueFebruaryTenTwoThousandTwentyThreeMember" name="FixedRateOfFivePointFourNinePercentBalloonDueFebruaryTenTwoThousandTwentyThreeMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointOneThreePercentageBalloonDueJuneTwentyFourTwoThousandTwentyThreeMember" name="FixedRateOfFourPointOneThreePercentageBalloonDueJuneTwentyFourTwoThousandTwentyThreeMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FloatingInterestRateOfOnePointOneSixFivePercentLIBORPlusBalloonDueAugustTwoTwoThousandTwentyThreeMember" name="FloatingInterestRateOfOnePointOneSixFivePercentLIBORPlusBalloonDueAugustTwoTwoThousandTwentyThreeMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointSevenTwoPercentBalloonDueFebruaryThirteenTwoThousandTwentyFourMember" name="FixedRateOfFourPointSevenTwoPercentBalloonDueFebruaryThirteenTwoThousandTwentyFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFiveEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyFourMember" name="FixedRateOfFourPointFiveEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FloatingInterestRateOfOnePointFourZeroPercentLIBORPlusBalloonDueJuneThirteenTwoThousandTwentyFourMember" name="FloatingInterestRateOfOnePointFourZeroPercentLIBORPlusBalloonDueJuneThirteenTwoThousandTwentyFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointThreeOnePercentBalloonDueJuneTwentyFourTwoThousandTwentyFiveMember" name="FixedRateOfFourPointThreeOnePercentBalloonDueJuneTwentyFourTwoThousandTwentyFiveMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointEightFivePercentBalloonDueFebruaryThirteenTwoThousandTwentySixMember" name="FixedRateOfFourPointEightFivePercentBalloonDueFebruaryThirteenTwoThousandTwentySixMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointSevenThreePercentBalloonDueFebruaryTwentySevenTwoThousandTwentySixMember" name="FixedRateOfFourPointSevenThreePercentBalloonDueFebruaryTwentySevenTwoThousandTwentySixMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFourZeroPercentBalloonDueJuneTwoTwoThousandTwentySixMember" name="FixedRateOfFourPointFourZeroPercentBalloonDueJuneTwoTwoThousandTwentySixMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointThreeSixPercentBalloonDueJuneTwentyFourTwoThousandTwentySixMember" name="FixedRateOfFourPointThreeSixPercentBalloonDueJuneTwentyFourTwoThousandTwentySixMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfThreePointSevenFivePercentBalloonDueJanuaryThirtyTwoThousandTwentySevenMember" name="FixedRateOfThreePointSevenFivePercentBalloonDueJanuaryThirtyTwoThousandTwentySevenMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointZeroNinePercentBalloonDueJuneTwentySevenTwoThousandTwentySevenMember" name="FixedRateOfFourPointZeroNinePercentBalloonDueJuneTwentySevenTwoThousandTwentySevenMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointZeroNinePercentBalloonDueAugustTwoTwoThousandTwentySevenMember" name="FixedRateOfFourPointZeroNinePercentBalloonDueAugustTwoTwoThousandTwentySevenMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointOneFourPercentBalloonDueAugustFourTwoThousandTwentySevenMember" name="FixedRateOfFourPointOneFourPercentBalloonDueAugustFourTwoThousandTwentySevenMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfThreePointFourSixPercentageBalloonDueDecemberOneTwoThousandTwentySevenMember" name="FixedRateOfThreePointFourSixPercentageBalloonDueDecemberOneTwoThousandTwentySevenMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFiveFivePercentBalloonDueJuneTwoTwoThousandTwentyEightMember" name="FixedRateOfFourPointFiveFivePercentBalloonDueJuneTwoTwoThousandTwentyEightMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointThreeFourPercentBalloonDueJuneThirteenTwoThousandTwentyEightMember" name="FixedRateOfFourPointThreeFourPercentBalloonDueJuneThirteenTwoThousandTwentyEightMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFivePointZeroFourPercentageBalloonDueFebruaryThirteenTwoThousandTwentyNineMember" name="FixedRateOfFivePointZeroFourPercentageBalloonDueFebruaryThirteenTwoThousandTwentyNineMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointNineEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyNineMember" name="FixedRateOfFourPointNineEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyNineMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointOneNinePercentBalloonDueJuneTwentySevenTwoThousandTwentyNineMember" name="FixedRateOfFourPointOneNinePercentBalloonDueJuneTwentySevenTwoThousandTwentyNineMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointOneNinePercentBalloonDueAugustTwoTwoThousandTwentyNineMember" name="FixedRateOfFourPointOneNinePercentBalloonDueAugustTwoTwoThousandTwentyNineMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfThreePointFourEightPercentBalloonDueDecemberTwoTwothousandTwentyNineMember" name="FixedRateOfThreePointFourEightPercentBalloonDueDecemberTwoTwothousandTwentyNineMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfThreePointNineNinePercentBalloonDueJanuaryThirtyTwoThousandThirtyMember" name="FixedRateOfThreePointNineNinePercentBalloonDueJanuaryThirtyTwoThousandThirtyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFourFourPercentBalloonDueJuneThirteenTwoThousandThirtyMember" name="FixedRateOfFourPointFourFourPercentBalloonDueJuneThirteenTwoThousandThirtyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFivePointOneFourPercentBalloonDueMarchThirteenTwoThousandThirtyOneMember" name="FixedRateOfFivePointOneFourPercentBalloonDueMarchThirteenTwoThousandThirtyOneMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointSevenZeroPercentBalloonDueJuneTwoTwoThousandThirtyOneMember" name="FixedRateOfFourPointSevenZeroPercentBalloonDueJuneTwoTwoThousandThirtyOneMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointZeroNinePercentBalloonDueJanuaryThirtyTwoThousandThirtyTwoMember" name="FixedRateOfFourPointZeroNinePercentBalloonDueJanuaryThirtyTwoThousandThirtyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointThreeFourPercentBalloonDueJuneTwentySevenTwoThousandThirtyTwoMember" name="FixedRateOfFourPointThreeFourPercentBalloonDueJuneTwentySevenTwoThousandThirtyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointThreeFourPercentBalloonDueAugustTwoTwoThousandThirtyTwoMember" name="FixedRateOfFourPointThreeFourPercentBalloonDueAugustTwoTwoThousandThirtyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFiveNinePercentBalloonDueJuneThirteenTwoThousandThirtyThreeMember" name="FixedRateOfFourPointFiveNinePercentBalloonDueJuneThirteenTwoThousandThirtyThreeMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFivePointTwoNinePercentBalloonDueMarchThirteenTwoThousandThirtyFourMember" name="FixedRateOfFivePointTwoNinePercentBalloonDueMarchThirteenTwoThousandThirtyFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFourEightPercentBalloonDueJuneTwelveTwoThousandThirtyFourMember" name="FixedRateOfFourPointFourEightPercentBalloonDueJuneTwelveTwoThousandThirtyFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointTwoFourPercentBalloonDueJanuaryThirtyTwoThousandThirtyFiveMember" name="FixedRateOfFourPointTwoFourPercentBalloonDueJanuaryThirtyTwoThousandThirtyFiveMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointSixNinePercentBalloonDueJuneThirteenTwoThousandThirtyEightMember" name="FixedRateOfFourPointSixNinePercentBalloonDueJuneThirteenTwoThousandThirtyEightMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFivePointFourFivePercentBalloonDueMarchThirteenTwoThousandThirtyNineMember" name="FixedRateOfFivePointFourFivePercentBalloonDueMarchThirteenTwoThousandThirtyNineMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFourNinePercentBalloonDueJanuaryThirtyTwoThousandFortyMember" name="FixedRateOfFourPointFourNinePercentBalloonDueJanuaryThirtyTwoThousandFortyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_PrimeOrLiborPlusUpToOnePointFourFivePercentExpiresJuneSevenTwoThousandTwentyFourMember" name="PrimeOrLiborPlusUpToOnePointFourFivePercentExpiresJuneSevenTwoThousandTwentyFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InterbankRatePlusOnePointFourZeroZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" name="InterbankRatePlusOnePointFourZeroZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InterbankRatePlusOnePointSevenFiveZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" name="InterbankRatePlusOnePointSevenFiveZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InterbankRatePlusZeroPointSevenThreeZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" name="InterbankRatePlusZeroPointSevenThreeZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InterbankRatePlusZeroPointNineFourZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" name="InterbankRatePlusZeroPointNineFourZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InterbankRatesExpiresSeptemberFifteenTwoThousandTwentyTwoMember" name="InterbankRatesExpiresSeptemberFifteenTwoThousandTwentyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NotePurchaseAgreementMember" name="NotePurchaseAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UnsecuredMulticurrencyCreditAgreementMember" name="UnsecuredMulticurrencyCreditAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AudDenominatedTrancheMember" name="AudDenominatedTrancheMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NzdDenominatedTrancheMember" name="NzdDenominatedTrancheMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FacilityBMember" name="FacilityBMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FacilityCAndFacilityDMember" name="FacilityCAndFacilityDMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_PremiumFinancingDebtFacilityMember" name="PremiumFinancingDebtFacilityMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DebtInstrumentPrepaymentDate" name="DebtInstrumentPrepaymentDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_CreditAgreementMember" name="CreditAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_SeniorUnsecuredNoteMember" name="SeniorUnsecuredNoteMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateSeniorUnsecuredNotesMember" name="FixedRateSeniorUnsecuredNotesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UnsecuredNotesMember" name="UnsecuredNotesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_SeriesKNotesMember" name="SeriesKNotesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_SeriesCNotesMember" name="SeriesCNotesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfThreePointSevenFivePercentDueTwoThousandTwentySevenMember" name="FixedRateOfThreePointSevenFivePercentDueTwoThousandTwentySevenMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointZeroNinePercentDueTwoThousandThirtyMember" name="FixedRateOfFourPointZeroNinePercentDueTwoThousandThirtyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointZeroNinePercentDueTwoThousandThirtyTwoMember" name="FixedRateOfFourPointZeroNinePercentDueTwoThousandThirtyTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointTwoFourDueTwoThousandThirtyFiveMember" name="FixedRateOfFourPointTwoFourDueTwoThousandThirtyFiveMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOfFourPointFourNineDueTwoThousandFortyMember" name="FixedRateOfFourPointFourNineDueTwoThousandFortyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DebtInstrumentMaturityYear" name="DebtInstrumentMaturityYear" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_AmountPayableToRedeemNotesPercentOfPrincipalAmount" name="AmountPayableToRedeemNotesPercentOfPrincipalAmount" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DiscountRateUsedToComputeRemainingScheduledPaymentsOfPrincipalAndInterest" name="DiscountRateUsedToComputeRemainingScheduledPaymentsOfPrincipalAndInterest" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_NumberOfFinancialInstitutionsEnteredInUnsecuredMulticurrencyCreditAgreement" name="NumberOfFinancialInstitutionsEnteredInUnsecuredMulticurrencyCreditAgreement" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_AmendmentTypeAxis" name="AmendmentTypeAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AmendmentTypeDomain" name="AmendmentTypeDomain" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_BeforeAmendmentMember" name="BeforeAmendmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AfterAmendmentMember" name="AfterAmendmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CreditFacilityTwoMember" name="CreditFacilityTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CreditFacilityThreeMember" name="CreditFacilityThreeMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CreditFacilityFourMember" name="CreditFacilityFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FixedRateOverLibor" name="FixedRateOverLibor" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_AnnualFacilityFeeOfRevolvingCreditFacility" name="AnnualFacilityFeeOfRevolvingCreditFacility" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DebtAcquisitionCosts" name="DebtAcquisitionCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ProceedsFromDebtFacilityVariableLimits" name="ProceedsFromDebtFacilityVariableLimits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_InterestRateTermDebtTransactions" name="InterestRateTermDebtTransactions" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_WeightedAverageNumberOfCommonAndCommonEquivalentSharesOutstanding" name="WeightedAverageNumberOfCommonAndCommonEquivalentSharesOutstanding" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_StockOptionPlansLineItems" name="StockOptionPlansLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AnnualActivityOfStockOptionPlansTable" name="AnnualActivityOfStockOptionPlansTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_LongTermIncentivePlanMember" name="LongTermIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandSeventeenLongTermincentivePlanMember" name="TwoThousandSeventeenLongTermincentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_BlackScholesOptionPricingModelMember" name="BlackScholesOptionPricingModelMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NumberOfPeriodsOptionsExpire" name="NumberOfPeriodsOptionsExpire" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ExercisePriceOfStockOptionsPercentOfFairMarketValueOfShareOfCommonStockOnDateOfGrant" name="ExercisePriceOfStockOptionsPercentOfFairMarketValueOfShareOfCommonStockOnDateOfGrant" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearOne" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearOne" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearTwo" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearTwo" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearThree" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearThree" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PeriodForOptionsToExpireFromDateOfGrant" name="PeriodForOptionsToExpireFromDateOfGrant" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_AgeOfEmployeeNoLongerSubjectToAwardForfeitureOnConditionCompliance" name="AgeOfEmployeeNoLongerSubjectToAwardForfeitureOnConditionCompliance" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PeriodOfServiceFromGrantDateStockOptionsAwardedNotSubjectToForfeiture" name="PeriodOfServiceFromGrantDateStockOptionsAwardedNotSubjectToForfeiture" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPerShare" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPerShare" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonVestedAndExpectedToVestNumberOfShares" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonVestedAndExpectedToVestNumberOfShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedAndExpectedToVestExercisableWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedAndExpectedToVestExercisableWeightedAverageExercisePrice" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm" name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_SharebasedCompensationArrangementNonVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" name="SharebasedCompensationArrangementNonVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodIntrinsicValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodIntrinsicValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_WeightedAveragePeriod" name="WeightedAveragePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_Range01Member" name="Range01Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_Range02Member" name="Range02Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_Range03Member" name="Range03Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_Range04Member" name="Range04Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_Range05Member" name="Range05Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_Range06Member" name="Range06Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DeferredEquityParticipationPlanDistributionsToKeyExecutivesAge" name="DeferredEquityParticipationPlanDistributionsToKeyExecutivesAge" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DeferredEquityParticipationSubPlanDistributionsRequisiteServiceDescription" name="DeferredEquityParticipationSubPlanDistributionsRequisiteServiceDescription" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DeferredEquityParticipationSubPlanDistributionsToKeyExecutivesAge" name="DeferredEquityParticipationSubPlanDistributionsToKeyExecutivesAge" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ScheduleOfSaleOfSubsidiaryAbstract" name="ScheduleOfSaleOfSubsidiaryAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InvestmentsAndEmployeeDeferredCompensationPlanLineItems" name="InvestmentsAndEmployeeDeferredCompensationPlanLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InvestmentsAndEmployeeDeferredCompensationPlanTable" name="InvestmentsAndEmployeeDeferredCompensationPlanTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DeferredEquityParticipationPlanMember" name="DeferredEquityParticipationPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DeferredEquityParticipationPlanSubPlansMember" name="DeferredEquityParticipationPlanSubPlansMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DeferredCashParticipationPlanMember" name="DeferredCashParticipationPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CompensationApprovedByCommitteeValue" name="CompensationApprovedByCommitteeValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ProceedsFromSubPlan" name="ProceedsFromSubPlan" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_UnearnedDeferredCompensationValue" name="UnearnedDeferredCompensationValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_UnearnedDeferredCompensationShare" name="UnearnedDeferredCompensationShare" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_CashAndEquityAwardWithAggregateFairValueVestedAndDistributedToParticipants" name="CashAndEquityAwardWithAggregateFairValueVestedAndDistributedToParticipants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationLineItems" name="CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationTable" name="CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UnvestedRestrictedStockMember" name="UnvestedRestrictedStockMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandSeventeenPerformanceShareAwardsMember" name="TwoThousandSeventeenPerformanceShareAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CashAwardsMember" name="CashAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandTwentyProvisionalCashAwardsMember" name="TwoThousandTwentyProvisionalCashAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandNineteenProvisionalCashAwardsMember" name="TwoThousandNineteenProvisionalCashAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandEighteenProvisionalCashAwardsMember" name="TwoThousandEighteenProvisionalCashAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandSixteenProvisionalCashAwardsMember" name="TwoThousandSixteenProvisionalCashAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandFifteenProvisionalCashAwardsMember" name="TwoThousandFifteenProvisionalCashAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandFourteenProvisionalCashAwardsMember" name="TwoThousandFourteenProvisionalCashAwardsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingDate" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_VestingPeriodLineItems" name="VestingPeriodLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_VestingPeriodTable" name="VestingPeriodTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_VestingPeriodOneYearMember" name="VestingPeriodOneYearMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_VestingPeriodTwoYearsMember" name="VestingPeriodTwoYearsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_VestingPeriodFiveYearsMember" name="VestingPeriodFiveYearsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionNonvestedIntrinsicValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionNonvestedIntrinsicValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeValue" name="ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeUnits" name="ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeUnits" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_UltimateAwardValueMultiplesOfOriginalValueOfUnitsMinimum" name="UltimateAwardValueMultiplesOfOriginalValueOfUnitsMinimum" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_UltimateAwardValueMultiplesOfOriginalValueOfUnitsMaximum" name="UltimateAwardValueMultiplesOfOriginalValueOfUnitsMaximum" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_CashBasedCompensationAwardExpenses" name="CashBasedCompensationAwardExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_DefinedBenefitPlanNetAmountIncludedInRetainedEarning" name="DefinedBenefitPlanNetAmountIncludedInRetainedEarning" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationExpectedLongTermReturnOnPlanAssets" name="DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationExpectedLongTermReturnOnPlanAssets" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ExpectedPeriodOfReturnOnPlanAssets" name="ExpectedPeriodOfReturnOnPlanAssets" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_QualifiedContributorySavingsAndThriftFourZeroOneKPlanMember" name="QualifiedContributorySavingsAndThriftFourZeroOneKPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NonQualifiedDeferredCompensationPlanMember" name="NonQualifiedDeferredCompensationPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DefinedBenefitPlansUnrealizedGainsLosses" name="DefinedBenefitPlansUnrealizedGainsLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_DefinedBenefitPlanPercentageOfEligibleCompensationForMatchingContributionsByEmployer" name="DefinedBenefitPlanPercentageOfEligibleCompensationForMatchingContributionsByEmployer" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_MatchingContributionsVestingSchedule" name="MatchingContributionsVestingSchedule" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DefinedBenefitPlanAdditionalPercentageOfEligibleCompensationForMatchingContributionsByEmployer" name="DefinedBenefitPlanAdditionalPercentageOfEligibleCompensationForMatchingContributionsByEmployer" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_EquityMethodInvestmentSummarizedFinancialInformationFundingCommitments" name="EquityMethodInvestmentSummarizedFinancialInformationFundingCommitments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_ChemModLLCMember" name="ChemModLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ChemModInternationalLlcMember" name="ChemModInternationalLlcMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CleanCoalInvestmentsMember" name="CleanCoalInvestmentsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_VentureCapitalFundsAndOtherMember" name="VentureCapitalFundsAndOtherMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ControllingInterestMember" name="ControllingInterestMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FourteenTwoThousandNineEraCleanCoalProductionPlantsMember" name="FourteenTwoThousandNineEraCleanCoalProductionPlantsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_OneTwoThousandElevenEraCleanCoalProductionPlantsMember" name="OneTwoThousandElevenEraCleanCoalProductionPlantsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwentyTwoThousandElevenEraCleanCoalProductionPlantsMember" name="TwentyTwoThousandElevenEraCleanCoalProductionPlantsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NumberOfCoalPlants" name="NumberOfCoalPlants" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_ChemModCleanCoalVentureUsAndCanadianOperationsMember" name="ChemModCleanCoalVentureUsAndCanadianOperationsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ChemModCleanCoalVentureMember" name="ChemModCleanCoalVentureMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CQuestCleanCoalVentureGlobalOperationsMember" name="CQuestCleanCoalVentureGlobalOperationsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_EquityMethodInvestmentRevenuesOfLimitedLiabilityCompanies" name="EquityMethodInvestmentRevenuesOfLimitedLiabilityCompanies" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_EquityMethodInvestmentExpensesOfLimitedLiabilityCompanies" name="EquityMethodInvestmentExpensesOfLimitedLiabilityCompanies" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_NumberOfCleanCoalProductionPlantsOwned" name="NumberOfCleanCoalProductionPlantsOwned" type="xbrli:positiveIntegerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_TwoThousandNineEraPlantsMember" name="TwoThousandNineEraPlantsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_TwoThousandElevenEraPlantsMember" name="TwoThousandElevenEraPlantsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_LongTermProductionContractsMember" name="LongTermProductionContractsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NumberOfVariableInterestEntities" name="NumberOfVariableInterestEntities" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_EquityMethodInvestmentAssetsOfLimitedLiabilityCompanies" name="EquityMethodInvestmentAssetsOfLimitedLiabilityCompanies" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_EquityMethodInvestmentLiabilitiesOfLimitedLiabilityCompanies" name="EquityMethodInvestmentLiabilitiesOfLimitedLiabilityCompanies" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_NumberOfVentureCapitalFundsInvestment" name="NumberOfVentureCapitalFundsInvestment" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_NumberOfCertifiedLowIncomeHousingDevelopmentsInvestment" name="NumberOfCertifiedLowIncomeHousingDevelopmentsInvestment" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_CarryingValueOfInvestments" name="CarryingValueOfInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_Investment1Axis" name="Investment1Axis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_Investment1Domain" name="Investment1Domain" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FourVentureCapitalFundsMember" name="FourVentureCapitalFundsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_EightCertifiedLowIncomeHousingDevelopmentsMember" name="EightCertifiedLowIncomeHousingDevelopmentsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" name="CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_OperatingLeaseLiabilityNotYetCommenced" name="OperatingLeaseLiabilityNotYetCommenced" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_AccruedCompensationAndOtherCurrentLiabilitiesMember" name="AccruedCompensationAndOtherCurrentLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AmountOfGainLossRecognizedEffectivenessTesting" name="AmountOfGainLossRecognizedEffectivenessTesting" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_CommissionRevenueMember" name="CommissionRevenueMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CompensationExpenseMember" name="CompensationExpenseMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CommitmentsContingenciesAndOffBalanceSheetArrangementsLineItems" name="CommitmentsContingenciesAndOffBalanceSheetArrangementsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CommitmentsContingenciesAndOffBalanceSheetArrangementsTable" name="CommitmentsContingenciesAndOffBalanceSheetArrangementsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_InterestOnDebtMember" name="InterestOnDebtMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_DebtObligationMember" name="DebtObligationMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_OperatingLeaseObligationMember" name="OperatingLeaseObligationMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_SubleaseArrangementsMember" name="SubleaseArrangementsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_OutstandingPurchaseObligationsMember" name="OutstandingPurchaseObligationsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ContractualObligationsMember" name="ContractualObligationsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_RecordedUnconditionalPurchaseObligationReceivableWithinOneYear" name="RecordedUnconditionalPurchaseObligationReceivableWithinOneYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RecordedUnconditionalPurchaseObligationReceivableInSecondYear" name="RecordedUnconditionalPurchaseObligationReceivableInSecondYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RecordedUnconditionalPurchaseObligationReceivableInThirdYear" name="RecordedUnconditionalPurchaseObligationReceivableInThirdYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RecordedUnconditionalPurchaseObligationReceivableInFourthYear" name="RecordedUnconditionalPurchaseObligationReceivableInFourthYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RecordedUnconditionalPurchaseObligationReceivableInFifthYear" name="RecordedUnconditionalPurchaseObligationReceivableInFifthYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RecordedUnconditionalPurchaseObligationReceivableAfterFifthYear" name="RecordedUnconditionalPurchaseObligationReceivableAfterFifthYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_RecordedUnconditionalPurchaseObligationReceivable" name="RecordedUnconditionalPurchaseObligationReceivable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_TaxIncrementFinancingMember" name="TaxIncrementFinancingMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UnconsolidatedInvestmentsInEnterprisesMember" name="UnconsolidatedInvestmentsInEnterprisesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_SelfInsuranceDeductiblesMember" name="SelfInsuranceDeductiblesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_RentCaptiveFacilityMember" name="RentCaptiveFacilityMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_SecurityDepositMember" name="SecurityDepositMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ErrorsAndOmissionsMember" name="ErrorsAndOmissionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UpToFourPointFiveMillionMember" name="UpToFourPointFiveMillionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UpToTenMillionMember" name="UpToTenMillionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UpToTwentyPointZeroMillionMember" name="UpToTwentyPointZeroMillionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_UpToTwentySevenPointZeroMillionMember" name="UpToTwentySevenPointZeroMillionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NumberOfSquareFeet" name="NumberOfSquareFeet" type="num:areaItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_NumberOfEmployees" name="NumberOfEmployees" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_PropertyTaxCreditExpectToReceive" name="PropertyTaxCreditExpectToReceive" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_EconomicDevelopmentForGrowingEconomyTaxCredit" name="EconomicDevelopmentForGrowingEconomyTaxCredit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_PropertyTaxCreditsReceivablePeriod" name="PropertyTaxCreditsReceivablePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearOne" name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearOne" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearTwo" name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearTwo" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThree" name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThree" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFour" name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFour" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFive" name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFive" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThereafter" name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThereafter" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitments" name="AmountOfCommitmentExpirationOffBalanceSheetCommitments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_LettersOfCreditMember" name="LettersOfCreditMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NumberOfLetterOfCreditIssued" name="NumberOfLetterOfCreditIssued" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="ajg_LiabilitiesRecordedOnSelfInsurance" name="LiabilitiesRecordedOnSelfInsurance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_Collateral" name="Collateral" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_CompensationForCommitments" name="CompensationForCommitments" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_CreditSupportUnderLettersOfCreditForDeductiblesDueByUsOnOurOwnInsuranceCoverageExpiresAfterTwoThousandAndTwentyFiveMember" name="CreditSupportUnderLettersOfCreditForDeductiblesDueByUsOnOurOwnInsuranceCoverageExpiresAfterTwoThousandAndTwentyFiveMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CreditEnhancementUnderLettersOfCreditForOurCaptiveInsuranceOperationsToMeetMinimumStatutoryCapitalRequirementsExpiresAfterTwoThousandAndTwentyFiveMember" name="CreditEnhancementUnderLettersOfCreditForOurCaptiveInsuranceOperationsToMeetMinimumStatutoryCapitalRequirementsExpiresAfterTwoThousandAndTwentyFiveMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CollateralToClaimFundsHeldInFiduciaryCapacityByRecentAcquisitionExpiresTwoThousandTwentyOneMember" name="CollateralToClaimFundsHeldInFiduciaryCapacityByRecentAcquisitionExpiresTwoThousandTwentyOneMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_CreditSupportUnderLettersOfCreditInLieuOfSecurityDepositForAcquisitionLeaseExpiresTwoThousandAndTwentyFiveMember" name="CreditSupportUnderLettersOfCreditInLieuOfSecurityDepositForAcquisitionLeaseExpiresTwoThousandAndTwentyFiveMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_FinancialGuaranteesOfLoansToFiveCanadianBasedEmployeesTriggerMember" name="FinancialGuaranteesOfLoansToFiveCanadianBasedEmployeesTriggerMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_MicroCaptiveInsuranceCompaniesManaged" name="MicroCaptiveInsuranceCompaniesManaged" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_IncomeTaxExpenseBenefitLineItems" name="IncomeTaxExpenseBenefitLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_IncomeTaxExpenseBenefitTable" name="IncomeTaxExpenseBenefitTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_NoncurrentLiabilitiesMember" name="NoncurrentLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_GeneralBusinessAndOtherMember" name="GeneralBusinessAndOtherMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_HROneMember" name="HROneMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_EffectiveIncomeTaxRateReconciliationOtherPermanentDifferences" name="EffectiveIncomeTaxRateReconciliationOtherPermanentDifferences" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_IncreaseDecreaseInEffectiveIncomeTaxRateReconciliationRepatriationOfForeignEarnings" name="IncreaseDecreaseInEffectiveIncomeTaxRateReconciliationRepatriationOfForeignEarnings" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_EffectiveIncomeTaxRateReconciliationChangesInUnrecognizedTaxBenefitsRelatedToResolutionOfFederalAndStateAuditsExpirationOfVariousStatutesOfLimitationsAndOtherItems" name="EffectiveIncomeTaxRateReconciliationChangesInUnrecognizedTaxBenefitsRelatedToResolutionOfFederalAndStateAuditsExpirationOfVariousStatutesOfLimitationsAndOtherItems" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DeferredTaxAssetsAlternativeMinimumTaxAndOtherCreditCarryforwards" name="DeferredTaxAssetsAlternativeMinimumTaxAndOtherCreditCarryforwards" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_DeferredTaxAssetsAccruedAndUnfundedCompensationAndEmployeeBenefits" name="DeferredTaxAssetsAccruedAndUnfundedCompensationAndEmployeeBenefits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_DeferredTaxAssetsAccruedPensionLiability" name="DeferredTaxAssetsAccruedPensionLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_DeferredTaxAssetsLeaseLiabilities" name="DeferredTaxAssetsLeaseLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="ajg_DeferredTaxLiabilitiesInvestmentRelatedPartnerships" name="DeferredTaxLiabilitiesInvestmentRelatedPartnerships" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_DeferredTaxLiabilitiesDepreciableFixedAssets" name="DeferredTaxLiabilitiesDepreciableFixedAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_DeferredTaxLiabilitiesRightOfUseAsset" name="DeferredTaxLiabilitiesRightOfUseAsset" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_DeferredTaxLiabilitiesRevenueRecognition" name="DeferredTaxLiabilitiesRevenueRecognition" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_DeferredTaxLiabilitiesOtherPrepaidItems" name="DeferredTaxLiabilitiesOtherPrepaidItems" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_DeferredTaxAssetsTaxCreditCarryforwardExpirationYear" name="DeferredTaxAssetsTaxCreditCarryforwardExpirationYear" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_DeferredTaxAssetsOperatingLossCarryforwardExpirationYear" name="DeferredTaxAssetsOperatingLossCarryforwardExpirationYear" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="ajg_NetGainsLossesOnDivestituresMember" name="NetGainsLossesOnDivestituresMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_ValuationAllowancesAndReservesAdditionsChargedToEarnings" name="ValuationAllowancesAndReservesAdditionsChargedToEarnings" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="ajg_AllowanceForEstimatedPolicyCancellationsMember" name="AllowanceForEstimatedPolicyCancellationsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="ajg_AccumulatedAmortizationOfExpirationListsNonCompeteAgreementsAndTradeNamesMember" name="AccumulatedAmortizationOfExpirationListsNonCompeteAgreementsAndTradeNamesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
</xsd:schema>
