-----BEGIN PRIVACY-ENHANCED MESSAGE-----
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,
 PSnCGZv/gi+B0aCk6rAU9Bz6JXJrZ+G5fdPN+dXO57FC/KhtGUg9E4IPvTmEh+RM
 EM56kO7yVcI8ZVjRVJqUuA==

<SEC-DOCUMENT>0001179110-04-023153.txt : 20041214
<SEC-HEADER>0001179110-04-023153.hdr.sgml : 20041214
<ACCEPTANCE-DATETIME>20041214130845
ACCESSION NUMBER:		0001179110-04-023153
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041210
FILED AS OF DATE:		20041214
DATE AS OF CHANGE:		20041214

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GLASSELL CLAES
		CENTRAL INDEX KEY:			0001192617

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21937
		FILM NUMBER:		041200862

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		2018043011

	MAIL ADDRESS:	
		STREET 1:		C/O CAMBREX CORP
		STREET 2:		ONE MEADOWLANDS PLZ
		CITY:			EAST RUTHERFORD
		STATE:			NJ
		ZIP:			07073

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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-12-10</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001020214</issuerCik>
        <issuerName>CERUS CORP</issuerName>
        <issuerTradingSymbol>CERS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001192617</rptOwnerCik>
            <rptOwnerName>GLASSELL CLAES</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CERUS CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>2411 STANWELL DRIVE</rptOwnerStreet2>
            <rptOwnerCity>CONCORD</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94520</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Officer and Director</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.89</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-12-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>100000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-12-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Option vests monthly over 48 months, beginning on December 10, 2004.</footnote>
        <footnote id="F2">Innaplicable.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Lori Roll, Attorney-in-Fact</signatureName>
        <signatureDate>2004-12-13</signatureDate>
    </ownerSignature>
</ownershipDocument>

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