<SUBMISSION>
<ACCESSION-NUMBER>0001032235-03-000009
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20030912
<FILING-DATE>20030912
<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>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>TREFLER ALAN
<CIK>0001032235
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-11859
<FILM-NUMBER>03893584
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>C/O PEGASYSTEMS INC
<STREET2>101 MAIN STREET
<CITY>CAMBRIDGE
<STATE>MA
<ZIP>02142
<PHONE>6173749600
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>C/O PEGASYSTEMS INC
<STREET2>101 MAIN STREET
<CITY>CAMBRIDGE
<STATE>MA
<ZIP>02142
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
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        <issuerTradingSymbol>PEGA</issuerTradingSymbol>
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            <rptOwnerStreet2>101 MAIN STREET</rptOwnerStreet2>
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            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02142</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
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        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO &amp; Chairman of the Board</officerTitle>
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    </nonDerivativeTable>



    <ownerSignature>
        <signatureName>June M. Morris, Esq., as Attorney-in-Fact for Alan Trefler</signatureName>
        <signatureDate>2003-09-12</signatureDate>
    </ownerSignature>

</ownershipDocument>

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