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        <link:definition>9954483 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</link:definition>
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        <link:definition>9954485 - Disclosure - REVENUE (Disaggregation of Revenue by Major Product and Service Categories) (Details)</link:definition>
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        <link:definition>9954486 - Disclosure - REVENUE (Disaggregation of Revenue by Principal Geographic Area, Based on Customers' Domiciles) (Details)</link:definition>
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        <link:definition>9954487 - Disclosure - REVENUE (Free or Discounted Instruments and Systems) (Details)</link:definition>
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        <link:definition>9954488 - Disclosure - REVENUE (Up-Front Consideration Paid to Customers) (Details)</link:definition>
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        <link:definition>9954489 - Disclosure - REVENUE (Rebate Arrangements) (Details)</link:definition>
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  <xs:element id="idxx_TreasuryStockAcquiredAverageCostPerShareEmployeeSurrenders" abstract="false" name="TreasuryStockAcquiredAverageCostPerShareEmployeeSurrenders" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:perShareItemType"/>
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  <xs:element id="idxx_CAGDiagnosticCapitalInstrumentsMember" abstract="false" name="CAGDiagnosticCapitalInstrumentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
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  <xs:element id="idxx_DeferredStockUnitsMember" abstract="false" name="DeferredStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
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</xs:schema>
