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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 D4XHF/2r4ZOvUhHF41WPYzwau54oe5uRSWak6jhxb/7vbSYuf25yXW4GIgErOP0Q
 EkQrsQ0zIoWcfyPOX/6kqw==

<SEC-DOCUMENT>0001307009-08-000001.txt : 20081003
<SEC-HEADER>0001307009-08-000001.hdr.sgml : 20081003
<ACCEPTANCE-DATETIME>20081003121341
ACCESSION NUMBER:		0001307009-08-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20081001
FILED AS OF DATE:		20081003
DATE AS OF CHANGE:		20081003

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			IDEX CORP /DE/
		CENTRAL INDEX KEY:			0000832101
		STANDARD INDUSTRIAL CLASSIFICATION:	PUMPS & PUMPING EQUIPMENT [3561]
		IRS NUMBER:				363555336
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		630 DUNDEE RD STE 400
		CITY:			NORTHBROOK
		STATE:			IL
		ZIP:			60062
		BUSINESS PHONE:		8474987070

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HERMANCE FRANK S
		CENTRAL INDEX KEY:			0001190203

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-10235
		FILM NUMBER:		081105854

	BUSINESS ADDRESS:	
		STREET 1:		C/O AMTEK INC
		STREET 2:		37 NORTH VALLEY RD BLDG 4
		CITY:			PAOLI
		STATE:			PA
		ZIP:			19301
		BUSINESS PHONE:		6106472121
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-10-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000832101</issuerCik>
        <issuerName>IDEX CORP /DE/</issuerName>
        <issuerTradingSymbol>IEX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001190203</rptOwnerCik>
            <rptOwnerName>HERMANCE FRANK S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>DEFERRED COMPENSATION UNITS (DCU'S)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>341</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>COMMON STOCK</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>341</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6458</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">CREDITS FOR DIVIDENDS ON DCU BALANCE AND DEFERRED CASH COMPENSATION UNDER THE SECOND AMENDED AND RESTATED IDEX CORPORATION DIRECTORS DEFERRED COMPENSATION PLAN AT A PRICE PER DCU RANGING FROM $38.87 TO $31.02. EACH DCU IS EXCHANGEABLE FOR SHARES OF IDEX CORPORATION COMMON STOCK ON A ONE-FOR-ONE BASIS FIVE YEARS AFTER THE YEAR FOR WHICH COMPENSATION IS DEFERRED.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>FRANK S. HERMANCE</signatureName>
        <signatureDate>2008-10-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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