-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 0vU4bEu2ge5WWl2uLL13rA==

<SEC-DOCUMENT>0001362118-09-000001.txt : 20090129
<SEC-HEADER>0001362118-09-000001.hdr.sgml : 20090129
<ACCEPTANCE-DATETIME>20090129152710
ACCESSION NUMBER:		0001362118-09-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090128
FILED AS OF DATE:		20090129
DATE AS OF CHANGE:		20090129

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			PUDIL MICHAEL J
		CENTRAL INDEX KEY:			0001249249

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-00619
		FILM NUMBER:		09554391

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		763-295-9202

	MAIL ADDRESS:	
		STREET 1:		213 CHELSEA ROAD
		CITY:			MONTICELLO
		STATE:			MN
		ZIP:			55362

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			WSI INDUSTRIES, INC.
		CENTRAL INDEX KEY:			0000104897
		STANDARD INDUSTRIAL CLASSIFICATION:	METALWORKING MACHINERY & EQUIPMENT [3540]
		IRS NUMBER:				410691607
		STATE OF INCORPORATION:			MN
		FISCAL YEAR END:			0828

	BUSINESS ADDRESS:	
		STREET 1:		213 CHELSEA ROAD
		CITY:			MONTICELLO
		STATE:			MN
		ZIP:			55362
		BUSINESS PHONE:		763-295-9202

	MAIL ADDRESS:	
		STREET 1:		213 CHELSEA ROAD
		CITY:			MONTICELLO
		STATE:			MN
		ZIP:			55362

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	WSI INDUSTRIES INC
		DATE OF NAME CHANGE:	19990113

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	WASHINGTON SCIENTIFIC INDUSTRIES INC
		DATE OF NAME CHANGE:	19920703
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-01-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000104897</issuerCik>
        <issuerName>WSI INDUSTRIES, INC.</issuerName>
        <issuerTradingSymbol>WSCI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001249249</rptOwnerCik>
            <rptOwnerName>PUDIL MICHAEL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>213 CHELSEA ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MONTICELLO</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55362</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Executive Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-01-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>30000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.4748</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>78642</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Getey M. Ritchott, Attorney-in-Fact for Michael J. Pudil</signatureName>
        <signatureDate>2009-01-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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