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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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 7qkDUfP91jmiKsd5MhIOlw==

<SEC-DOCUMENT>0001127602-08-004056.txt : 20080609
<SEC-HEADER>0001127602-08-004056.hdr.sgml : 20080609
<ACCEPTANCE-DATETIME>20080609140703
ACCESSION NUMBER:		0001127602-08-004056
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080605
FILED AS OF DATE:		20080609
DATE AS OF CHANGE:		20080609

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			OSI PHARMACEUTICALS INC
		CENTRAL INDEX KEY:			0000729922
		STANDARD INDUSTRIAL CLASSIFICATION:	IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES [2835]
		IRS NUMBER:				133159796
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		41 PINELAWN ROAD
		CITY:			MELVILLE
		STATE:			NY
		ZIP:			11747
		BUSINESS PHONE:		631-962-2000

	MAIL ADDRESS:	
		STREET 1:		41 PINELAWN ROAD
		CITY:			MELVILLE
		STATE:			NY
		ZIP:			11747

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ONCOGENE SCIENCE INC
		DATE OF NAME CHANGE:	19920703

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SIMON ROBERT L
		CENTRAL INDEX KEY:			0001220050

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-15190
		FILM NUMBER:		08887662

	MAIL ADDRESS:	
		STREET 1:		58 S SERVICE RD
		CITY:			MELVILLE
		STATE:			NY
		ZIP:			11747
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-06-05</periodOfReport>

    <issuer>
        <issuerCik>0000729922</issuerCik>
        <issuerName>OSI PHARMACEUTICALS INC</issuerName>
        <issuerTradingSymbol>OSIP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001220050</rptOwnerCik>
            <rptOwnerName>SIMON ROBERT L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OSI PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>41 PINELAWN ROAD</rptOwnerStreet2>
            <rptOwnerCity>MELVILLE</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>11747</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Exec. VP, Pharm. Dev. &amp; Manf.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2300</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>21.50</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>27376</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2300</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25076</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>21.55</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2300</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-06-12</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-06-11</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2300</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>11500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Transaction made pursuant to a 10b5-1 plan effective as of May 1, 2008.</footnote>
        <footnote id="F2">Includes the following shares acquired under the OSI Employee Stock Purchase Plan: (i) 125 shares acquired on December 31, 2007; and (ii) 170 shares acquired on March 31, 2008.</footnote>
        <footnote id="F3">One third of the stock option became exercisable one year after the date of the grant and the remainder vested ratably on a monthly basis over the succeeding 24 months.</footnote>
        <footnote id="F4">Includes only options with the same termination date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Michael G. Atieh, attorney-in-fact for Mr. Simon</signatureName>
        <signatureDate>2008-06-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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