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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001316360-11-000006.txt : 20110118
<SEC-HEADER>0001316360-11-000006.hdr.sgml : 20110117
<ACCEPTANCE-DATETIME>20110118184311
ACCESSION NUMBER:		0001316360-11-000006
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20110113
FILED AS OF DATE:		20110118
DATE AS OF CHANGE:		20110118

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Green Stephen
		CENTRAL INDEX KEY:			0001324614

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32511
		FILM NUMBER:		11534211

	MAIL ADDRESS:	
		STREET 1:		C/O DAVIS POLK & WARDWELL
		STREET 2:		450 LEXINGTON AVENUE
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			IHS Inc.
		CENTRAL INDEX KEY:			0001316360
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROGRAMMING, DATA PROCESSING, ETC. [7370]
		IRS NUMBER:				133769440
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1130

	BUSINESS ADDRESS:	
		STREET 1:		15 INVERNESS WAY EAST
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80112
		BUSINESS PHONE:		303-790-0600

	MAIL ADDRESS:	
		STREET 1:		15 INVERNESS WAY EAST
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80112
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-01-13</periodOfReport>

    <issuer>
        <issuerCik>0001316360</issuerCik>
        <issuerName>IHS Inc.</issuerName>
        <issuerTradingSymbol>IHS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001324614</rptOwnerCik>
            <rptOwnerName>Green Stephen</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IHS INC.</rptOwnerStreet1>
            <rptOwnerStreet2>15 INVERNESS WAY EAST</rptOwnerStreet2>
            <rptOwnerCity>ENGLEWOOD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80112</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr VP, General Counsel</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2011-01-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6160</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>43960</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2011-01-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2297</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>79.27</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>41663</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This award represents performance-based restricted stock units that were vested on January 13, 2011, based upon the determination of the Human Resources Committee of the Board of Directors that certain financial performance goals were achieved.</footnote>
        <footnote id="F2">Represents shares withheld for taxes upon vesting of performance-based restricted stock units.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ M. Sean Radcliffe, Attorney-in-Fact on behalf of Reporting Person</signatureName>
        <signatureDate>2011-01-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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