-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 RsOpbWcA8K1ieJppp9sNBHr7lQRs0wVWLYTuk6ylgrTPIPdGjVv6u18JUIMyNG9U
 F/c4fZhUIHEruP34Yo40HA==

<SEC-DOCUMENT>0001179110-06-023766.txt : 20061218
<SEC-HEADER>0001179110-06-023766.hdr.sgml : 20061218
<ACCEPTANCE-DATETIME>20061218170429
ACCESSION NUMBER:		0001179110-06-023766
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20061218
FILED AS OF DATE:		20061218
DATE AS OF CHANGE:		20061218

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MCCORMACK ROBERT C
		CENTRAL INDEX KEY:			0001143959

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-04797
		FILM NUMBER:		061284088

	MAIL ADDRESS:	
		STREET 1:		C/O WESTVACO CORP
		STREET 2:		299 PARK AVENUE
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ILLINOIS TOOL WORKS INC
		CENTRAL INDEX KEY:			0000049826
		STANDARD INDUSTRIAL CLASSIFICATION:	GENERAL INDUSTRIAL MACHINERY & EQUIPMENT [3560]
		IRS NUMBER:				361258310
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		3600 W LAKE AVE
		CITY:			GLENVIEW
		STATE:			IL
		ZIP:			60025-5811
		BUSINESS PHONE:		8476574106

	MAIL ADDRESS:	
		STREET 1:		3600 WEST LAKE AVENUE
		CITY:			GLENVIEW
		STATE:			IL
		ZIP:			60025-5811
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-12-18</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000049826</issuerCik>
        <issuerName>ILLINOIS TOOL WORKS INC</issuerName>
        <issuerTradingSymbol>ITW</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001143959</rptOwnerCik>
            <rptOwnerName>MCCORMACK ROBERT C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>228 SOUTH BEACH ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOBE SOUND</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33455</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-12-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>80800</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>47.0668</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7202318</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Trust</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4858914</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>In Trusts</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6200</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares held in trusts of which the Reporting Person is a co-trustee and in which a member of his immediate family (adult not living in his household) has a pecuniary interest.  The Reporting Person disclaims beneficial ownership of these shares.</footnote>
        <footnote id="F2">Shares held in trusts of which the Reporting Person is a co-trustee and has a pecuniary interest.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Bruce F. McKenzie using P.O.A. for Robert C. McCormack</signatureName>
        <signatureDate>2006-12-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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