-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 OCdpDvXuWhWvv9GYmJRj6I0I62OSf9m64k9mtRImBbMOFu/xZ7TYNSpEQevuk7TH
 XCj1nzGCYh4W1qHtekhVrA==

<SEC-DOCUMENT>0001253532-04-000013.txt : 20040305
<SEC-HEADER>0001253532-04-000013.hdr.sgml : 20040305
<ACCEPTANCE-DATETIME>20040305164427
ACCESSION NUMBER:		0001253532-04-000013
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040304
FILED AS OF DATE:		20040305

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MIDGLEY C EDWARD
		CENTRAL INDEX KEY:			0001016651

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21109
		FILM NUMBER:		04652590

	MAIL ADDRESS:	
		STREET 1:		25 MATTHIGSSEN PARK
		CITY:			IRVINGTON
		STATE:			NY
		ZIP:			10533

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>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-03-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001016651</rptOwnerCik>
            <rptOwnerName>MIDGLEY C EDWARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <transactionDate>
                <value>2004-03-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>C. Edward Midgley</signatureName>
        <signatureDate>2004-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>

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