-----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,
 WvcjH4G2Z3XhRBFlXj7eBoB7BxEgUB/H8vkDChUxWwRg9DLWnC2Z17ZxR4Hy4gqg
 0fw0tya28B2EbJ37RNdLiA==

<SEC-DOCUMENT>0001179110-03-003325.txt : 20030710
<SEC-HEADER>0001179110-03-003325.hdr.sgml : 20030710
<ACCEPTANCE-DATETIME>20030709182207
ACCESSION NUMBER:		0001179110-03-003325
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030707
FILED AS OF DATE:		20030710

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ADAPTEC INC
		CENTRAL INDEX KEY:			0000709804
		STANDARD INDUSTRIAL CLASSIFICATION:	COMPUTER COMMUNICATIONS EQUIPMENT [3576]
		IRS NUMBER:				942748530
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		691 S MILPITAS BLVD
		STREET 2:		M/S25
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035
		BUSINESS PHONE:		4089458600

	MAIL ADDRESS:	
		STREET 1:		691 SOUTH MILPITAS BLVD
		STREET 2:		M/S25
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MOHR MARSHALL
		CENTRAL INDEX KEY:			0001252986

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-15071
		FILM NUMBER:		03780845

	BUSINESS ADDRESS:	
		STREET 1:		691 S. MILPITAS BLVD
		STREET 2:		C/O ADAPTEC INC
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035
		BUSINESS PHONE:		4089458600

	MAIL ADDRESS:	
		STREET 1:		C/O ADAPTEC INC
		STREET 2:		691 S. MILPITAS BLVD
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 3 -
<TEXT>
<XML>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>3</documentType>
<periodOfReport>2003-07-07</periodOfReport>
    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000709804</issuerCik>
        <issuerName>ADAPTEC INC</issuerName>
        <issuerTradingSymbol>adpt</issuerTradingSymbol>
</issuer>
<reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001252986</rptOwnerCik>
            <rptOwnerName>MOHR MARSHALL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector>
<isOfficer>1</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle>Vice President and CFO</officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeSecurity><securityTitle><value>Common Stock</value>
</securityTitle>
<transactionAmounts><transactionShares><value>0</value>
</transactionShares>
</transactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
</directOrIndirectOwnership>
</ownershipNature>
</nonDerivativeSecurity>
<nonDerivativeSecurity><securityTitle><value>Common Stock</value>
</securityTitle>
<transactionAmounts><transactionShares><value>0</value>
</transactionShares>
</transactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>I</value>
</directOrIndirectOwnership>
<natureOfOwnership><value>None.</value>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeSecurity>
<footnotes></footnotes>
<ownerSignature><signatureName>Marshall Mohr</signatureName>
<signatureDate>2003-07-09</signatureDate>
</ownerSignature>
</ownershipDocument>

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