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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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 DRx+CHzXm7y/SvFQQlEZPg==

<SEC-DOCUMENT>0001222645-03-000002.txt : 20030617
<SEC-HEADER>0001222645-03-000002.hdr.sgml : 20030617
<ACCEPTANCE-DATETIME>20030617144840
ACCESSION NUMBER:		0001222645-03-000002
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030616
FILED AS OF DATE:		20030617

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WINGER DENNIS L
		CENTRAL INDEX KEY:			0001222645

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19119
		FILM NUMBER:		03747190

	BUSINESS ADDRESS:	
		STREET 1:		APPLERA CORP, CELERA GEOMICS GROUP
		STREET 2:		45 WEST GUDE DR
		CITY:			ROCKVILLE
		STATE:			MD
		ZIP:			20850
		BUSINESS PHONE:		2404533000

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CEPHALON INC
		CENTRAL INDEX KEY:			0000873364
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				232484489
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		145 BRANDYWINE PKWY
		CITY:			WEST CHESTER
		STATE:			PA
		ZIP:			19380
		BUSINESS PHONE:		6103440200

	MAIL ADDRESS:	
		STREET 1:		145 BRANDYWINE PARKWAY
		CITY:			WEST CHESTER
		STATE:			PA
		ZIP:			19380
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <documentType>4</documentType>

    <periodOfReport>2003-06-16</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000873364</issuerCik>
        <issuerName>CEPHALON INC</issuerName>
        <issuerTradingSymbol>CEPH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001222645</rptOwnerCik>
            <rptOwnerName>WINGER DENNIS L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeSecurity>
        <securityTitle>
            <value>Non-Qualified Stock Option</value>
        </securityTitle>
        <conversionOrExercisePrice>
            <value>45.38</value>
        </conversionOrExercisePrice>
        <transactionDate>
            <value>2003-06-16</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>A</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>15000</value>
            </transactionShares>
            <transactionValue>
                <value>0</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <exerciseDate>
            <value>2004-06-16</value>
            <footnoteId id="F1"/>
        </exerciseDate>
        <expirationDate>
            <value>2013-06-16</value>
        </expirationDate>
        <underlyingSecurity>
            <underlyingSecurityTitle>
                <value>Common Stock</value>
            </underlyingSecurityTitle>
            <underlyingSecurityShares>
                <value>15000</value>
            </underlyingSecurityShares>
        </underlyingSecurity>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>15000</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </derivativeSecurity>

    <footnotes>
        <footnote id="F1">The option vests in four equal installments, beginning on the first anniversary of the date of the grant, and is fully vested four years from the date of the grant.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Carolyn S. Iosca, Attorney-in-Fact, For: Dennis L. Winger</signatureName>
        <signatureDate>2003-06-17</signatureDate>
    </ownerSignature>

</ownershipDocument>

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