<SEC-DOCUMENT>0001179110-15-016798.txt : 20151230
<SEC-HEADER>0001179110-15-016798.hdr.sgml : 20151230
<ACCEPTANCE-DATETIME>20151230161617
ACCESSION NUMBER:		0001179110-15-016798
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20151210
FILED AS OF DATE:		20151230
DATE AS OF CHANGE:		20151230

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:			HANDLEY THOMAS W
		CENTRAL INDEX KEY:			0001275967

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09328
		FILM NUMBER:		151313726

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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-12-10</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001275967</rptOwnerCik>
            <rptOwnerName>HANDLEY THOMAS W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>370 WABASHA STREET NORTH</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>President and COO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-12-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value>E</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>571</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26739.664</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19177.155</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By GRAT No. 1</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>51775</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By GRAT No. 2</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>548.044</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Ecolab Savings Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Number of UNITS in the Ecolab Stock Fund of the Ecolab Savings Plan (401(k) Plan) as of November 30, 2015. (The 548.044 UNITS are the equivalent of approximately 1,011 SHARES of the issuer's Common Stock.)</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ David F. Duvick, as Attorney-in-Fact for Thomas W. Handley</signatureName>
        <signatureDate>2015-12-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
