<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-02-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000761237</issuerCik>
        <issuerName>IMCOR PHARMACEUTICAL CO</issuerName>
        <issuerTradingSymbol>ICPH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001268459</rptOwnerCik>
            <rptOwnerName>DEAN RICHARD T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O PHOTGEN TECHNOLOGIES INC</rptOwnerStreet1>
            <rptOwnerStreet2>6175 LUSK BLVD</rptOwnerStreet2>
            <rptOwnerCity>SAN DEIGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92121</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Options (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.30</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-02-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>60000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.30</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-02-16</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>60000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>60000</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Compensation Committee and the Issuer's Board approved grants of non-qualified options to the Reporting Person on the terms described in Table II.  The options vest in accordance and are in other aspects subject to stock option award agreements.</footnote>
        <footnote id="F2">On February 16, 2004, Mr. Dean was granted an option to acquire a total of 60,000 shares of common stock in IMCOR Pharmaceutical Co. pursuant to a letter agreement dated effective as of October 27, 2003; 7,500 shares vesting quarterly for eight quarters.  These options may terminate earlier under certain circumstances as set forth in Mr. Dean's award agreement.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Richard Dean</signatureName>
        <signatureDate>2004-02-16</signatureDate>
    </ownerSignature>
</ownershipDocument>

