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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 GU0s9ARxXjHJwnrnAmKP7g==

<SEC-DOCUMENT>0001140361-10-022412.txt : 20100520
<SEC-HEADER>0001140361-10-022412.hdr.sgml : 20100520
<ACCEPTANCE-DATETIME>20100520161558
ACCESSION NUMBER:		0001140361-10-022412
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100519
FILED AS OF DATE:		20100520
DATE AS OF CHANGE:		20100520

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SCHMERTZLER MICHAEL
		CENTRAL INDEX KEY:			0001288952

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-50633
		FILM NUMBER:		10848101

	MAIL ADDRESS:	
		STREET 1:		1300 VALLEY ROAD
		CITY:			NEW CANAAN
		STATE:			CT
		ZIP:			06840

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CYTOKINETICS INC
		CENTRAL INDEX KEY:			0001061983
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				943291317

	BUSINESS ADDRESS:	
		STREET 1:		280 EAST GRAND AVENUE
		STREET 2:		.
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
		BUSINESS PHONE:		(650) 624-3000

	MAIL ADDRESS:	
		STREET 1:		280 EAST GRAND AVENUE
		CITY:			SOUTH SAN FRANCISCO
		STATE:			CA
		ZIP:			94080
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-05-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001061983</issuerCik>
        <issuerName>CYTOKINETICS INC</issuerName>
        <issuerTradingSymbol>CYTK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001288952</rptOwnerCik>
            <rptOwnerName>SCHMERTZLER MICHAEL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CREDIT SUISSE</rptOwnerStreet1>
            <rptOwnerStreet2>ELEVEN MADISON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10010</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, par value $0.001</value>
            </securityTitle>
            <transactionDate>
                <value>2010-05-19</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>16239</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.00</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4403913</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote 2</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the average per share sale price.</footnote>
        <footnote id="F2">The post transaction share total of 4,403,913 is represented by the following: (a) 3,278,221 shares of Common Stock held by Credit Suisse First Boston Equity Partners, L.P.; (b) 916,345 shares of Common Stock held by Credit Suisse First Boston Equity Partners (Bermuda), L.P.; (c) 2,916 shares of Common Stock held by Credit Suisse First Boston U.S. Executive Advisors, L.P.; (d) 88,766 shares of Common Stock held by EMA Partners Fund 2000, L.P.; and (e) 117,665 shares of Common Stock held by EMA Private Equity Fund 2000, L.P. Such amounts include shares of Common Stock issuable upon exercise of warrants previously reported in May 2009. Mr. Schmertzler is a Managing Director of Aries Advisors, LLC, the sub-advisor to Credit Suisse First Boston Equity Partners, L.P. Mr. Schmertzler disclaims beneficial ownership of the shares held by entities affiliated with Credit Suisse except to the extent of his proportionate partnership or membership interest, if any, therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Michael Schmertzler</signatureName>
        <signatureDate>2010-05-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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