-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 LtpBv2TCVGK5qaQmLJC7x8ZbQfsybv78TCo2x6KEWfN9pZsbLzqZ4kRZfHJ3RSL2
 erTx1t41EYWh6q8uDyMo0Q==

<SEC-DOCUMENT>0001127602-10-016858.txt : 20100609
<SEC-HEADER>0001127602-10-016858.hdr.sgml : 20100609
<ACCEPTANCE-DATETIME>20100609173756
ACCESSION NUMBER:		0001127602-10-016858
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100607
FILED AS OF DATE:		20100609
DATE AS OF CHANGE:		20100609

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			LEUNG GABRIEL
		CENTRAL INDEX KEY:			0001236183

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-15190
		FILM NUMBER:		10888550

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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-06-07</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001236183</rptOwnerCik>
            <rptOwnerName>LEUNG GABRIEL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OSI PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>420 SAW MILL RIVER RD.</rptOwnerStreet2>
            <rptOwnerCity>ARDSLEY</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10502</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>EVP &amp; Pres. Pharma. Business</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-06-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>U</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>910</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>57.50</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes></footnotes>

    <ownerSignature>
        <signatureName>/s/ Pierre Legault, attorney-in-fact for Mr. Leung</signatureName>
        <signatureDate>2010-06-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----