-----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,
 ONP/8JCVBjGmhLSAMYKVgZrZD6r8DUQ3SWfPDva4BFeopxOJSEM2myHdnz/KhD4N
 AWzMaVs22O6WHV8523cIrw==

<SEC-DOCUMENT>0001072343-10-000047.txt : 20100301
<SEC-HEADER>0001072343-10-000047.hdr.sgml : 20100301
<ACCEPTANCE-DATETIME>20100301164100
ACCESSION NUMBER:		0001072343-10-000047
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100226
FILED AS OF DATE:		20100301
DATE AS OF CHANGE:		20100301

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CAVANAGH RICHARD
		CENTRAL INDEX KEY:			0001075522

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14601
		FILM NUMBER:		10645096

	MAIL ADDRESS:	
		STREET 1:		100 BELLEVUE PARKWAY
		CITY:			WILMINGTON
		STATE:			DE
		ZIP:			19809

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ARCH CHEMICALS INC
		CENTRAL INDEX KEY:			0001072343
		STANDARD INDUSTRIAL CLASSIFICATION:	CHEMICALS & ALLIED PRODUCTS [2800]
		IRS NUMBER:				061526315
		STATE OF INCORPORATION:			VA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		501 MERRITT 7
		STREET 2:		P O BOX 4500
		CITY:			NORWALK
		STATE:			CT
		ZIP:			06856-4500
		BUSINESS PHONE:		2037503729

	MAIL ADDRESS:	
		STREET 1:		501 MERRITT 7
		STREET 2:		P O BOX 4500
		CITY:			NORWALK
		STATE:			CT
		ZIP:			06856-4500
</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>2010-02-26</periodOfReport>

    <issuer>
        <issuerCik>0001072343</issuerCik>
        <issuerName>ARCH CHEMICALS INC</issuerName>
        <issuerTradingSymbol>ARJ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001075522</rptOwnerCik>
            <rptOwnerName>CAVANAGH RICHARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARCH CHEMICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>501 MERRITT 7</rptOwnerStreet2>
            <rptOwnerCity>NORWALK</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06851</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock $1 Par Value</value>
            </securityTitle>
            <transactionDate>
                <value>2010-02-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>18.04</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7323</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock $1 Par Value</value>
            </securityTitle>
            <transactionDate>
                <value>2010-02-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.92</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3723</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-Employee Director Stock Option (Right To Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>18.04</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2010-02-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2001-01-02</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-12-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3600</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Joseph P. Lacerenza, Attorney in Fact</signatureName>
        <signatureDate>2010-03-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----