<?xml version="1.0"?>

<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-08-05</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001035688</issuerCik>
        <issuerName>SELECT MEDICAL CORP</issuerName>
        <issuerTradingSymbol>SEM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000918697</rptOwnerCik>
            <rptOwnerName>ORTENZIO ROBERT A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4716 OLD GETTYSBURG ROAD</rptOwnerStreet1>
            <rptOwnerStreet2>P.O. BOX 2034</rptOwnerStreet2>
            <rptOwnerCity>MECHANICSBURG</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>17055</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO and President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>

        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2003-08-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2036</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6799</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Select Investments I</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>

    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Pro rata distribution from Golder, Thoma, Cressey, Rauner Fund V, L.P., of which Select Investments I is a limited partner.  Mr. Ortenzio is a partner and 25% owner of Select Investments I.  Mr. Ortenzio disclaims beneficial ownership of any shares held by Select Investments I that exceed his pecuniary interest therein.</footnote>
        <footnote id="F2">Mr. Ortenzio also indirectly beneficially owns 13,740 shares held directly by Select Capital Corporation.  Mr. Ortenzio is a 25% owner, Director and President of Select Capital Corporation.  Mr. Ortenzio also indirectly beneficially owns 500 shares held directly by Select Healthcare Investors I, L.P.  Mr. Ortenzio is a 25% owner, Director and President of Select Capital Corporation, the general partner of Select Healthcare Investors I, L.P.  Mr. Ortenzio disclaims beneficial ownership of any shares held by Select Capital Corporation and Select Healthcare Investors I, L.P. that exceed his pecuniary interest therein.</footnote>
        <footnote id="F3">Mr. Ortenzio also indirectly beneficially owns 65,695 shares held directly by the RAO Generation Skipping Trust, of which Mr. Ortenzio is a trustee and beneficiary.  Mr. Ortenzio also indirectly beneficially owns 44,169 shares held directly by the Ortenzio Family Partnership, L.P., of which Mr. Ortenzio is the general partner.  Mr. Ortenzio also indirectly beneficially owns 4,429 shares held directly by the R.A. Ortenzio Family Partnership, L.P., of which Mr. Ortenzio is a general partner.  Mr. Ortenzio disclaims beneficial ownership of any shares held by the R.A. Ortenzio Family Partnership, L.P. that exceed his pecuniary interest therein.  Mr. Ortenzio also owns 1,053,733 shares directly.</footnote>
    </footnotes>


    <ownerSignature>
        <signatureName>/s/ Robert A. Ortenzio</signatureName>
        <signatureDate>2003-08-07</signatureDate>
    </ownerSignature>

</ownershipDocument>

