<SEC-DOCUMENT>0001179110-17-006293.txt : 20170428
<SEC-HEADER>0001179110-17-006293.hdr.sgml : 20170428
<ACCEPTANCE-DATETIME>20170428173714
ACCESSION NUMBER:		0001179110-17-006293
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20161215
FILED AS OF DATE:		20170428
DATE AS OF CHANGE:		20170428

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 CORPORATE CENTER
		STREET 2:		370 WABASHA STREET NORTH
		CITY:			SAINT PAUL
		STATE:			MN
		ZIP:			55102
		BUSINESS PHONE:		6512502587

	MAIL ADDRESS:	
		STREET 1:		ECOLAB CORPORATE CENTER
		STREET 2:		370 WABASHA STREET NORTH
		CITY:			SAINT PAUL
		STATE:			MN
		ZIP:			55102

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ECOLAB INC
		DATE OF NAME CHANGE:	19920703

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Hickey Michael A
		CENTRAL INDEX KEY:			0001343364

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09328
		FILM NUMBER:		17797440

	MAIL ADDRESS:	
		STREET 1:		370 WABASHA STREET NORTH
		CITY:			ST PAUL
		STATE:			MN
		ZIP:			55102
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4/A -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2016-12-15</periodOfReport>

    <dateOfOriginalSubmission>2016-12-19</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001343364</rptOwnerCik>
            <rptOwnerName>Hickey Michael A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1 ECOLAB PLACE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAINT PAUL</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55102</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP &amp; Pres. Global Inst.</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>39876.065</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On December 19, 2016, the reporting person mistakenly filed a Form 4 reporting a December 15, 2016 gift of 619 shares of common stock that did not in fact occur. The 39,876.065 shares reported in column 5 above restores the number of shares of common stock directly owned by the reporting person as of December 15, 2016 to the pre-gift amount. Additionally, the Form 4 filed by the reporting person on February 24, 2017 to report two transactions occurring on February 22, 2017 was prepared prior to the realization that the gift of 619 shares did not in fact occur. Including those 619 shares, the reporting person directly owned 43,630.097 shares of common stock as of February 22, 2017 rather than the 43,011.097 shares reported on the February 24, 2017 Form 4.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ David F. Duvick, as Attorney-in-fact for Michael A. Hickey</signatureName>
        <signatureDate>2017-04-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
