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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 GT0h8AGAYqDtaiIkcLz4rw2Kh3F4YPZjJaFjZY19xdZqIvE6C0gjJU9OtEphBa/o
 S6ZuGQz515+AqOkWLwViYQ==

<SEC-DOCUMENT>0001433759-08-000006.txt : 20081121
<SEC-HEADER>0001433759-08-000006.hdr.sgml : 20081121
<ACCEPTANCE-DATETIME>20081121151436
ACCESSION NUMBER:		0001433759-08-000006
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20081120
FILED AS OF DATE:		20081121
DATE AS OF CHANGE:		20081121

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Ceyrolle Eric
		CENTRAL INDEX KEY:			0001373473

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-17869
		FILM NUMBER:		081207257

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		508-650-3000

	MAIL ADDRESS:	
		STREET 1:		C/O COGNEX CORPORATION
		STREET 2:		ONE VISION DRIVE
		CITY:			NATICK
		STATE:			MA
		ZIP:			01760-2059

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			COGNEX CORP
		CENTRAL INDEX KEY:			0000851205
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INSTRUMENTS FOR MEASUREMENT, DISPLAY, AND CONTROL [3823]
		IRS NUMBER:				042713778
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		ONE VISION DR
		CITY:			NATICK
		STATE:			MA
		ZIP:			01760
		BUSINESS PHONE:		5086503000

	MAIL ADDRESS:	
		STREET 1:		ONE VISION DRIVE
		CITY:			NATICK
		STATE:			MA
		ZIP:			01760
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgardoc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-11-20</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000851205</issuerCik>
        <issuerName>COGNEX CORP</issuerName>
        <issuerTradingSymbol>CGNX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001373473</rptOwnerCik>
            <rptOwnerName>Ceyrolle Eric</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>504 DAHLIA DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WAYLAND</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01778</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Ex  VP  WW Sales &amp; Marketing</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-11-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.76</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Eric Ceyrolle</signatureName>
        <signatureDate>2008-11-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----