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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 UmKJoswmcu2+FupO0++/8tBZljkwPtYERSXOOOdNMY1TjXoMicqFPNV/lem4FaL5
 Nkykz+BS17H15AyT4uRMaw==

<SEC-DOCUMENT>0001179110-08-017955.txt : 20081007
<SEC-HEADER>0001179110-08-017955.hdr.sgml : 20081007
<ACCEPTANCE-DATETIME>20081007175219
ACCESSION NUMBER:		0001179110-08-017955
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20081004
FILED AS OF DATE:		20081007
DATE AS OF CHANGE:		20081007

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			INVESTMENT TECHNOLOGY GROUP INC
		CENTRAL INDEX KEY:			0000920424
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		IRS NUMBER:				133757717
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		380 MADISON AVE
		STREET 2:		4TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017
		BUSINESS PHONE:		2125884000

	MAIL ADDRESS:	
		STREET 1:		380 MADISON AVE
		STREET 2:		4TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GASSER ROBERT C
		CENTRAL INDEX KEY:			0001023087

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32722
		FILM NUMBER:		081113002

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		2034258000

	MAIL ADDRESS:	
		STREET 1:		C/O NYFIX INC
		STREET 2:		333 LUDLOW ST
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06902
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-10-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000920424</issuerCik>
        <issuerName>INVESTMENT TECHNOLOGY GROUP INC</issuerName>
        <issuerTradingSymbol>ITG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001023087</rptOwnerCik>
            <rptOwnerName>GASSER ROBERT C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ITG INC.</rptOwnerStreet1>
            <rptOwnerStreet2>380 MADISON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10017</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO and President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-10-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3521</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>27.82</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>43226</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>400</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares withheld to satisfy the Reporting Person's tax withholding obligations.  Please refer to the Restricted Share Agreement between the Reporting Person and Investment Technology Group, Inc. dated October 4, 2006, filed with Form 10-Q on November 9, 2006. As a result of the achievement of the performance metric for this award, the number of shares as to which beneficial ownership was acquired was 31,250, of which 10,417 shares vested on 10/31/2007, and 10,417 shares vested on 10/4/2008, and the remaining shares are unvested.</footnote>
        <footnote id="F2">The shares of common stock are held in UTMA custodial accounts on behalf of the Reporting Person's children.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>P. Mats Goebels, by Power of Attorney filed with Form 4 dated April 18, 2007</signatureName>
        <signatureDate>2008-10-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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