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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 WAznYaCJj4LNSvwv/sWdBtzCCu2WJLOKxOYzMpJR2Iz0n6jc9W5VcFe+tsj++uyR
 Iz+UTQtofZKpaPoEfAvJVQ==

<SEC-DOCUMENT>0001179110-03-012602.txt : 20031215
<SEC-HEADER>0001179110-03-012602.hdr.sgml : 20031215
<ACCEPTANCE-DATETIME>20031215172807
ACCESSION NUMBER:		0001179110-03-012602
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031212
FILED AS OF DATE:		20031215

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CASSIN BJ
		CENTRAL INDEX KEY:			0001193205

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21937
		FILM NUMBER:		031055507

	MAIL ADDRESS:	
		STREET 1:		C/O CERUS CORP
		STREET 2:		2411 STENWELL DRIVE
		CITY:			CONCORD
		STATE:			CA
		ZIP:			94520

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CERUS CORP
		CENTRAL INDEX KEY:			0001020214
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				680262011
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2411 STANWELL DR
		CITY:			CONCORD
		STATE:			CA
		ZIP:			94520
		BUSINESS PHONE:		9252886000

	MAIL ADDRESS:	
		STREET 1:		2525 STANWELL DRIVE
		STREET 2:		STE 300
		CITY:			CONCORD
		STATE:			CA
		ZIP:			94520

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CERUS TECHNOLOGIES INC
		DATE OF NAME CHANGE:	19960731
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-12-12</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001020214</issuerCik>
        <issuerName>CERUS CORP</issuerName>
        <issuerTradingSymbol>CERS</issuerTradingSymbol>
</issuer>
<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001193205</rptOwnerCik>
            <rptOwnerName>CASSIN BJ</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3000 SAND HILL ROAD</rptOwnerStreet1>
            <rptOwnerStreet2>BUILDING 3, SUITE 210</rptOwnerStreet2>
            <rptOwnerCity>MENLO PARK</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94025</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value>
</securityTitle>
<transactionDate><value>2003-12-12</value>
</transactionDate>
<deemedExecutionDate><value>2003-12-12</value>
</deemedExecutionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>S</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionAmounts><transactionShares><value>9463</value>
</transactionShares>
<transactionPricePerShare><value>4.00</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>D</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>0</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>I</value>
</directOrIndirectOwnership>
<natureOfOwnership><value>By Partnership</value>
<footnoteId id="F1"></footnoteId>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeTransaction>
<nonDerivativeHolding><securityTitle><value>Common Stock</value>
</securityTitle>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>85000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>I</value>
</directOrIndirectOwnership>
<natureOfOwnership><value>By Foundation</value>
<footnoteId id="F2"></footnoteId>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeHolding>
<nonDerivativeHolding><securityTitle><value>Common Stock</value>
</securityTitle>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>382684</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>I</value>
</directOrIndirectOwnership>
<natureOfOwnership><value>By Trust</value>
<footnoteId id="F3"></footnoteId>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeHolding>
<nonDerivativeHolding><securityTitle><value>Common Stock</value>
</securityTitle>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>69841</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>I</value>
</directOrIndirectOwnership>
<natureOfOwnership><value>By Partnership</value>
<footnoteId id="F4"></footnoteId>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeHolding>
</nonDerivativeTable>
<derivativeTable></derivativeTable>
<footnotes><footnote id="F1">These securities are owned directly by Coral Group Inc. Escrow Agent FBO Partner Brendan Joseph Cassin and Isabel B. Cassin, Tr., UA 01/31/96, Cassin Family Trust.  The Reporting Person is a Trustee of such entity and disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.</footnote>
<footnote id="F2">These securities are beneficially owned directly by Cassin Educational Foundation.  The Reporting Person is the Chairman/President of such entity and disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.</footnote>
<footnote id="F3">These securities are beneficially owned directly by Brendan Joseph Cassin and Isabel B. Cassin, Tr., UA 01/31/96, Cassin Family Trust.  The Reporting Person is a Trustee of such entity and disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.</footnote>
<footnote id="F4">These securities are beneficially owned directly by Cassin Family Partnership.  The Reporting Person is a General Partner of such entity and disclaims beneficial ownership of these securities except to the extent of his proportionate partnership interest therein.</footnote>
</footnotes>
<ownerSignature><signatureName>B. J. Cassin</signatureName>
<signatureDate>2003-12-12</signatureDate>
</ownerSignature>
</ownershipDocument>

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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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