<SUBMISSION>
<ACCESSION-NUMBER>0001222573-03-000006
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20031114
<FILING-DATE>20031117
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>FRISCIA JOSEPH J
<CIK>0001222573
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-11859
<FILM-NUMBER>031007155
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>C/O PEGASYSTEMS INC
<STREET2>101 MAIN STREET
<CITY>CAMBRIDGE
<STATE>MA
<ZIP>02142
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>PEGASYSTEMS INC
<CIK>0001013857
<ASSIGNED-SIC>7374
<IRS-NUMBER>042787865
<STATE-OF-INCORPORATION>MA
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>101 MAIN ST
<CITY>CAMBRIDGE
<STATE>MA
<ZIP>02142-1590
<PHONE>6173749600
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>101 MAIN ST
<CITY>CAMBRIDGE
<STATE>MA
<ZIP>02142-1590
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
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    <periodOfReport>2003-11-14</periodOfReport>


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        <issuerName>PEGASYSTEMS INC</issuerName>
        <issuerTradingSymbol>PEGA</issuerTradingSymbol>
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            <rptOwnerName>FRISCIA JOSEPH J</rptOwnerName>
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            <rptOwnerStreet2>101 MAIN STREET</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02142</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive VP &amp; GM Apps</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

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        <nonDerivativeTransaction>
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                <value></value>
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                <transactionShares>
                    <value>1100</value>
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                <transactionPricePerShare>
                    <value>7.55</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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                <sharesOwnedFollowingTransaction>
                    <value>101883</value>
                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </nonDerivativeTransaction>

        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common</value>
            </securityTitle>
            <transactionDate>
                <value>2003-11-14</value>
            </transactionDate>
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                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <value></value>
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                <transactionShares>
                    <value>16283</value>
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                    <value>7.5</value>
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                    <value>D</value>
                </transactionAcquiredDisposedCode>
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                </sharesOwnedFollowingTransaction>
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                    <value>D</value>
                </directOrIndirectOwnership>
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    </nonDerivativeTable>

    <derivativeTable>

        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.3267</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2003-11-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>23500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <value>1994-12-29</value>
            </exerciseDate>
            <expirationDate>
                <value>2004-12-29</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>396000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
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                </sharesOwnedFollowingTransaction>
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        </derivativeTransaction>

    </derivativeTable>


    <remarks>1. 23,500 shares of common stock were exercised from a total grant of 396,000 shares of common stock and will vest in five equal installments beginning one year from the date of issue.</remarks>

    <ownerSignature>
        <signatureName>June M. Morris, Esq.,Attorney-in-Fact for Joseph J. Friscia</signatureName>
        <signatureDate>2003-11-17</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
