-----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,
 RViWTObGWejyQqJUhifHWw1QDeDOBbx4V+UpHu6wlWYuOWALg9BAUL4ny8Kzzwpv
 O0ETHIm8kxdcBUtqRYMCDQ==

<SEC-DOCUMENT>0001030317-03-000001.txt : 20030814
<SEC-HEADER>0001030317-03-000001.hdr.sgml : 20030814
<ACCEPTANCE-DATETIME>20030814120127
ACCESSION NUMBER:		0001030317-03-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030813
FILED AS OF DATE:		20030814

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CNS INC /DE/
		CENTRAL INDEX KEY:			0000814258
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTROMEDICAL & ELECTROTHERAPEUTIC APPARATUS [3845]
		IRS NUMBER:				411580270
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		PO BOX 39802
		CITY:			MINNEAPOLIS
		STATE:			MN
		ZIP:			55439
		BUSINESS PHONE:		6128206696

	MAIL ADDRESS:	
		STREET 1:		PO BOX 39802
		STREET 2:		PO BOX 39802
		CITY:			MINNEAPOLIS
		STATE:			MN
		ZIP:			55439

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			PERKINS RICHARD W
		CENTRAL INDEX KEY:			0001030317

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-16612
		FILM NUMBER:		03844708

	BUSINESS ADDRESS:	
		STREET 1:		730 EAST LAKE STREET
		CITY:			WAYZATA
		STATE:			MN
		ZIP:			55391
		BUSINESS PHONE:		6124738367

	MAIL ADDRESS:	
		STREET 1:		1120 WAYZATA BLVD E
		STREET 2:		STE 201
		CITY:			WAYZATA
		STATE:			MN
		ZIP:			55391
</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>2003-08-13</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000814258</issuerCik>
        <issuerName>CNS INC /DE/</issuerName>
        <issuerTradingSymbol>CNXS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001030317</rptOwnerCik>
            <rptOwnerName>PERKINS RICHARD W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1120 WAYZATA BLVD E</rptOwnerStreet1>
            <rptOwnerStreet2>STE 201</rptOwnerStreet2>
            <rptOwnerCity>WAYZATA</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55391</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>

        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2003-08-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.43</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>71039</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>

    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">57,039 shares reporting person sole trustee; 10,000 shares held in Perkins Capital Management Profit Sharing Plan; 4,000 shares reporting person sole shareholder.</footnote>
    </footnotes>


    <ownerSignature>
        <signatureName>Richard Perkins, by power of attorney</signatureName>
        <signatureDate>2003-08-14</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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