-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 JPCOBjConz0w8lyGW5KYBYc3HUIWV+e6t2jmUeAGOb1QzK+2Bj7Z75m8zAYXKseX
 WvF1TO1CMAKO9Ur+5WKlBw==

<SEC-DOCUMENT>0001253532-04-000045.txt : 20041215
<SEC-HEADER>0001253532-04-000045.hdr.sgml : 20041215
<ACCEPTANCE-DATETIME>20041215160226
ACCESSION NUMBER:		0001253532-04-000045
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041214
FILED AS OF DATE:		20041215
DATE AS OF CHANGE:		20041215

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DOINA ANTHONY C
		CENTRAL INDEX KEY:			0001253530

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21109
		FILM NUMBER:		041204957

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		2032388749

	MAIL ADDRESS:	
		STREET 1:		400 RESEARCH PARKWAY
		CITY:			MERIDEN
		STATE:			CT
		ZIP:			06450

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CUNO INC
		CENTRAL INDEX KEY:			0001019779
		STANDARD INDUSTRIAL CLASSIFICATION:	GENERAL INDUSTRIAL MACHINERY & EQUIPMENT, NEC [3569]
		IRS NUMBER:				061159240
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1031

	BUSINESS ADDRESS:	
		STREET 1:		400 RESEARCH PARKWAY
		CITY:			MERIDEN
		STATE:			CT
		ZIP:			06450
		BUSINESS PHONE:		2032375541

	MAIL ADDRESS:	
		STREET 1:		400 RESEARCH PARKWAY
		CITY:			MERIDEN
		STATE:			CT
		ZIP:			06450
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-12-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001019779</issuerCik>
        <issuerName>CUNO INC</issuerName>
        <issuerTradingSymbol>CUNO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001253530</rptOwnerCik>
            <rptOwnerName>DOINA ANTHONY C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>400 RESEARCH PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MERIDEN</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06450</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-12-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>102</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>63.19</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7752</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Anthony C. Doina</signatureName>
        <signatureDate>2004-12-15</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----