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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 F+RubE61Sx2lM0NbX1BMdwp4KUd4Eht1jCvadDsiQEA0bs7ShJw/zEERsbOi38c3
 F3XcyDRP41P1T2ZEJbuC0g==

<SEC-DOCUMENT>0001010499-04-000003.txt : 20040609
<SEC-HEADER>0001010499-04-000003.hdr.sgml : 20040609
<ACCEPTANCE-DATETIME>20040609175055
ACCESSION NUMBER:		0001010499-04-000003
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040609
FILED AS OF DATE:		20040609

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KEOUGH WILLIAM H
		CENTRAL INDEX KEY:			0001010499

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-11859
		FILM NUMBER:		04856770

	BUSINESS ADDRESS:	
		STREET 1:		60
		STREET 2:		60 STATE STREET 19TH FLOOR
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02109-1820
		BUSINESS PHONE:		6174224960

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			PEGASYSTEMS INC
		CENTRAL INDEX KEY:			0001013857
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROCESSING & DATA PREPARATION [7374]
		IRS NUMBER:				042787865
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		101 MAIN ST
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142-1590
		BUSINESS PHONE:		6173749600

	MAIL ADDRESS:	
		STREET 1:		101 MAIN ST
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142-1590
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2004-06-09</periodOfReport>

    <dateOfOriginalSubmission>2004-06-09</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001013857</issuerCik>
        <issuerName>PEGASYSTEMS INC</issuerName>
        <issuerTradingSymbol>PEGA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001010499</rptOwnerCik>
            <rptOwnerName>KEOUGH WILLIAM H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PEGASYSTEMS INC.</rptOwnerStreet1>
            <rptOwnerStreet2>101 MAIN STREET</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02142</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option Grant (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>8.595</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>15000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2004-06-03</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-06-03</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>15000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <remarks>The 15,000 options granted on June 3, 2004 were fully vested upon issuance.  The options granted are pursuant to the 2004 Long-Term Incentive Plan.</remarks>

    <ownerSignature>
        <signatureName>June M. Morris, Esq., as Attorney-in-Fact for William H. Keough</signatureName>
        <signatureDate>2004-06-09</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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