-----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,
 OmMYLqZuGPQ7JyOoNuYOz6V61XxoH30ru8tsNvvU+mbuCsCDlkztkexjqNLdiW4s
 Et+kgS9INCAqF9KJbpqFmA==

<SEC-DOCUMENT>0001179110-05-009235.txt : 20050509
<SEC-HEADER>0001179110-05-009235.hdr.sgml : 20050509
<ACCEPTANCE-DATETIME>20050509120240
ACCESSION NUMBER:		0001179110-05-009235
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050506
FILED AS OF DATE:		20050509
DATE AS OF CHANGE:		20050509

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ECOLAB INC
		CENTRAL INDEX KEY:			0000031462
		STANDARD INDUSTRIAL CLASSIFICATION:	SOAP, DETERGENT, CLEANING PREPARATIONS, PERFUMES, COSMETICS [2840]
		IRS NUMBER:				410231510
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		ECOLAB CTR
		STREET 2:		370 WABASHA ST NORTH
		CITY:			ST PAUL
		STATE:			MN
		ZIP:			55102
		BUSINESS PHONE:		6512932233

	MAIL ADDRESS:	
		STREET 1:		370 WABASHA ST NORTH
		CITY:			ST. PAUL
		STATE:			MN
		ZIP:			55102

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ECONOMICS LABORATORY INC
		DATE OF NAME CHANGE:	19861203

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			PRITCHARD BETH M
		CENTRAL INDEX KEY:			0001228598

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09328
		FILM NUMBER:		05810421

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		7344771100

	MAIL ADDRESS:	
		STREET 1:		BORDERS GROUP INC
		STREET 2:		100 PHOENIX DRIVE
		CITY:			ANN ARBOR
		STATE:			MI
		ZIP:			48108
</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>2005-05-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000031462</issuerCik>
        <issuerName>ECOLAB INC</issuerName>
        <issuerTradingSymbol>ECL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001228598</rptOwnerCik>
            <rptOwnerName>PRITCHARD BETH M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ORGANIZED LIVING, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>9851 LACKMAN ROAD</rptOwnerStreet2>
            <rptOwnerCity>LENEXA</rptOwnerCity>
            <rptOwnerState>KS</rptOwnerState>
            <rptOwnerZipCode>66219</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Director Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>32.57</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-05-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-05-06</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-05-06</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5600</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5600</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes></footnotes>

    <ownerSignature>
        <signatureName>/s/ David F. Duvick, as Attorney-in-Fact for Beth M. Pritchard</signatureName>
        <signatureDate>2005-05-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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