<SUBMISSION>
<ACCESSION-NUMBER>0001191731-03-000002
<TYPE>5/A
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20021231
<FILING-DATE>20030718
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>UJOBAI JOE
<CIK>0001191731
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>5/A
<ACT>34
<FILE-NUMBER>000-10200
<FILM-NUMBER>03791964
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>SEI INVESTMENT INC
<STREET2>ONE FREEDOM VALLEY
<CITY>OAKS
<STATE>PA
<ZIP>19456
</BUSINESS-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>SEI CORP
<CIK>0000350894
<ASSIGNED-SIC>6211
<IRS-NUMBER>231707341
<STATE-OF-INCORPORATION>PA
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>1 FREEDOM VALLEY DRIVE
<CITY>OAKS
<STATE>PA
<ZIP>19456-1100
<PHONE>6106761000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1 FREEDOM VALLEY DRIVE
<CITY>OAKS
<STATE>PA
<ZIP>19456-1100
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>5/A
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>5/A</documentType><periodOfReport>2002-12-31</periodOfReport><dateOfOriginalSubmission>2003-02-14</dateOfOriginalSubmission>
    <form3HoldingsReported>1</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000350894</issuerCik>
        <issuerName>SEI CORP</issuerName>
        <issuerTradingSymbol>SEIC</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001191731</rptOwnerCik>
            <rptOwnerName>UJOBAI JOE</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Senior Vice President</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionCoding><transactionFormType>3</transactionFormType></transactionCoding><transactionAmounts><transactionShares><value>155</value><footnoteId id="F1"/></transactionShares></transactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">The reporting person owned such shares on January 1, 2001, the date on which he became an officer of SEI Investment Company.  The shares were acquired under the SEI Stock Purchase Plan.</footnote></footnotes><ownerSignature><signatureName>Michelle Vaughn</signatureName><signatureDate>2003-07-17</signatureDate></ownerSignature></ownershipDocument>

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