<?xml version="1.0" encoding="utf-8"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
  <periodOfReport>2003-08-01</periodOfReport>
  <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001035688</issuerCik>
        <issuerName>SELECT MEDICAL CORP</issuerName>
        <issuerTradingSymbol>SEM</issuerTradingSymbol>
  </issuer>
  <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001072745</rptOwnerCik>
            <rptOwnerName>CRESSEY BRYAN C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CLARION TECHNOLOGIES INC</rptOwnerStreet1>
            <rptOwnerStreet2>235 CENTRAL AVE</rptOwnerStreet2>
            <rptOwnerCity>HOLLAND</rptOwnerCity>
            <rptOwnerState>MI</rptOwnerState>
            <rptOwnerZipCode>49423</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
      <isDirector>1</isDirector>
      <isOfficer>0</isOfficer>
      <isTenPercentOwner>0</isTenPercentOwner>
      <isOther>0</isOther>
    </reportingOwnerRelationship>
  </reportingOwner>
  <nonDerivativeTable>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>2029008</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See footnote</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>20288</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See footnote</value>
          <footnoteId id="F2"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>2378089</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See footnote</value>
          <footnoteId id="F3"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>5786</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See footnote</value>
          <footnoteId id="F4"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>5000</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.71</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>154373</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>2500</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.75</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>151873</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>5800</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.79</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>146073</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>15000</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.80</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>131073</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>200</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.81</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>130873</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>1800</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.82</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>129073</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>7200</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.83</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>121873</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>5000</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.84</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>116873</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>S</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>7500</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>28.85</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>109373</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See footnote</value>
          <footnoteId id="F5"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
  </nonDerivativeTable>
  <footnotes>
    <footnote id="F1">These shares are owned directly by Fund VI.  Mr. Cressey is a Principal of Thoma Cressey Equity Partners, Inc. ("TCEP"), which  is the general partner of TC Partners VI, L.P., which is the general partner of Fund VI.  The Reporting Person disclaims beneficial ownership except to the extent of his proportionate ownership interests therein.</footnote>
    <footnote id="F2">These shares are owned directly by Friends VI.  Mr. Cressey is a Principal of TCEP, which is the general partner of TC Partners VI, L.P., which is the general partner of Friends VI.  The Reporting Person disclaims beneficial ownership except to the extent of his proportionate ownership interests therein.  </footnote>
    <footnote id="F3">These shares are owned directly by  Golder, Thoma, Cressey, Rauner Fund V, L.P. ("Fund V").  Mr. Cressey is a Principal of GTCR Inc. which is the general partner of GTCR V, L.P., which is the general partner of Fund V.  The Reporting Person disclaims beneficial ownership except to the extent of his proportionate ownership interests therein.  </footnote>
    <footnote id="F4">These shares are owned directly by GTCR Associates V ("Associates V").  Mr. Cressey is a Principal of GTCR Inc., which is the managing general partner of Associates V.  The Reporting Person disclaims beneficial ownership except to the extent of his proportionate ownership interests therein.</footnote>
    <footnote id="F5">These shares are owned directly by Mr. Cressey.</footnote>
  </footnotes>
  <ownerSignature>
    <signatureName>Bryan C. Cressey</signatureName>
    <signatureDate>2003-08-05</signatureDate>
  </ownerSignature>
</ownershipDocument>

