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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-04-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001262294</rptOwnerCik>
            <rptOwnerName>FLEMING JONATHAN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OXFORD BIOSCIENCE PARTNERS</rptOwnerStreet1>
            <rptOwnerStreet2>222 BERKELEY STREET, SUITE 1650</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001286541</rptOwnerCik>
            <rptOwnerName>OBP MANAGEMENT IV LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>222 BERKELEY STREET, SUITE 1650</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2933334</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9414816</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Oxford Bioscience Partners IV L.P. and MRNA Fund II L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5200464</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14615280</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Oxford Bioscience Partners IV L.P. and MRNA Fund II L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>11693887</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26309167</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Oxford Bioscience Partners IV L.P. and MRNA Fund II L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Revolving Convertible Senior Secured Promissory Notes</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3900348</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Oxford Bioscience Partners IV L.P. and MRNA Fund II L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Secured Promissory Notes</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8770415.43</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Oxford Bioscience Partners IV L.P. and MRNA Fund II L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Warrants to purchase common stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-04-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1466668</value>
                    <footnoteId id="F6"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2004-04-14</value>
            </exerciseDate>
            <expirationDate>
                <value>2009-04-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1466668</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1466668</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Oxford Bioscience Partners IV L.P. and MRNA Fund II L.P.</value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Jonathan Fleming is the general partner of OBP Management IV L.P., which is the general partner of both Oxford Bioscience Partners IV L.P. (&quot;Oxford&quot;) and MRNA Fund II L.P (&quot;MRNA&quot;).  As such Mr. Fleming and OBP Management IV L.P. disclaim beneficial ownership except to the extent of their pecuniary interests.</footnote>
        <footnote id="F2">On April 14, 2004, Oxford and MRNA agreed to purchase an aggregate of 2,933,334 shares of common stock, 568,678 shares were issued to Oxford and 5,706 were issued to MRNA at the initial closing on April 19, 2004.  In connection with the second closing to occur no later than July 19, 2004, an additional 2,335,517 shares will be issued to Oxford and an additional 23,433 will be issued to MRNA.</footnote>
        <footnote id="F3">On April 14, 2004, Oxford and MRNA agreed to convert convertible notes in the aggregate amount of $3,900,348.  Of the aggregate amount of $3,900,348, Oxford agreed to convert principal of $3,623,644 and interest of $237,957.50, at a conversion price of $0.75 per share, which resulted in the acquisition of 5,148,802 shares of common stock.  Of the aggregate amount of $3,900,348, MRNA agreed to convert principal of $36,356 and interest of $2,390.50, at a conversion price of $0.75 per share, which resulted in the acquisition of 51,662 shares of common stock.  The convertible notes were convertible into common stock at a conversion price equal to the price of the common stock in a qualified equity financing at the same price on the same terms as securities sold to investors in such qualified equity financing.</footnote>
        <footnote id="F4">On April 19, 2004, Oxford and MRNA agreed to convert secured notes in the aggregate amount of $8,770,415.43.  Of the aggregate amount of $8,770,415.43, Oxford agreed to convert principal of $8,239,373.33 and interest of approximately $457,174.56, at a conversion price of $0.75 per share.  The conversion of the principal of Oxford's secured notes will result in the acquisition of 10,985,831 shares of common stock and the conversion of the interest of Oxford's secured notes will result in the acquisition of approximately 609,566 shares of common stock.  (continued in footnote 5)</footnote>
        <footnote id="F5">Of the aggregate amount of $8,770,415.43, MRNA agreed to convert principal of $70,126.67 and interest of approximately $3,740.87, at a conversion price of $0.75 per share. The conversion of the principal of MRNA's secured notes will result in the acquisition of 93,502 shares of common stock and the conversion of the interest will result in the acquisition of approximately 4,987 shares of common stock. The secured notes became convertible pursuant to a securities purchase agreement entered into on April 19, 2004.  The closing of the conversion of secured notes will occur no later than July 19, 2004.</footnote>
        <footnote id="F6">On April 14, 2004, Oxford and MRNA agreed to purchase warrants to purchase an aggregate of 1,466,668 shares of common stock, warrants to purchase 284,339 shares of common stock were issued to Oxford and warrants to purchase 2,853 shares of common stock were issued to MRNA at the initial closing on April 19, 2004. In connection with a second closing to occur no later than July 19, 2004, warrants to purchase an additional 1,167,759 shares will be issued to Oxford and warrants to purchase an additional 11,717 shares of common stock will be issued to MRNA.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Jonathan Fleming</signatureName>
        <signatureDate>2004-06-17</signatureDate>
    </ownerSignature>
</ownershipDocument>

