-----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,
 WTA0Ghv8wB/nS8W8skiUkHDPb0Wj8FU4eJmdCHTrJjUaoCiOEvdzb8GntKFu4lKI
 XcXCQG1ZYwfT7gyb3c2I1Q==

<SEC-DOCUMENT>0001144692-05-000004.txt : 20050517
<SEC-HEADER>0001144692-05-000004.hdr.sgml : 20050517
<ACCEPTANCE-DATETIME>20050517213603
ACCESSION NUMBER:		0001144692-05-000004
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050325
FILED AS OF DATE:		20050517
DATE AS OF CHANGE:		20050517

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Schwartz Kenneth Steven
		CENTRAL INDEX KEY:			0001326667

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-16335
		FILM NUMBER:		05840140

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		7324466831

	MAIL ADDRESS:	
		STREET 1:		26 NAVAJO  ROAD
		CITY:			MANALAPAN
		STATE:			NJ
		ZIP:			07726

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			RIDGEFIELD ACQUISITION CORP
		CENTRAL INDEX KEY:			0000812152
		STANDARD INDUSTRIAL CLASSIFICATION:	BLANK CHECKS [6770]
		IRS NUMBER:				840922701
		STATE OF INCORPORATION:			CO
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		900 THIRD AVE
		STREET 2:		SUITE 201
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
		BUSINESS PHONE:		3033680401

	MAIL ADDRESS:	
		STREET 1:		900 THIRD AVE
		STREET 2:		SUITE 201
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	BIO MEDICAL AUTOMATION INC
		DATE OF NAME CHANGE:	19990323

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	OZO DIVERSIFIED AUTOMATION INC /CO/
		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>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-03-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000812152</issuerCik>
        <issuerName>RIDGEFIELD ACQUISITION CORP</issuerName>
        <issuerTradingSymbol>rgda</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001326667</rptOwnerCik>
            <rptOwnerName>Schwartz Kenneth Steven</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>26 NAVAJO  ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MANALAPAN</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07726</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.16</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-03-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-03-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-03-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">These stock options were issued to Mr. Schwarz as consideration for his services as an independent director of the Issuer</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Kenneth Schwartz</signatureName>
        <signatureDate>2005-05-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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