-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 DTkgG3w4d3bl+V+bQrmlVZYbiZ/eCuCxsSMnsnnl34HuufsbsC2j6IktrwPjsvD2
 AUwTV1UplQEscIXRxuxVeg==

<SEC-DOCUMENT>0001179110-05-017863.txt : 20050912
<SEC-HEADER>0001179110-05-017863.hdr.sgml : 20050912
<ACCEPTANCE-DATETIME>20050912193542
ACCESSION NUMBER:		0001179110-05-017863
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050909
FILED AS OF DATE:		20050912
DATE AS OF CHANGE:		20050912

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WONG KENWAY
		CENTRAL INDEX KEY:			0001250007

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21236
		FILM NUMBER:		051080902

	BUSINESS ADDRESS:	
		STREET 1:		400 W CALIFORNIA AVENUE
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94086
		BUSINESS PHONE:		4087491888

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			APPLIED SIGNAL TECHNOLOGY INC
		CENTRAL INDEX KEY:			0000741696
		STANDARD INDUSTRIAL CLASSIFICATION:	COMMUNICATIONS EQUIPMENT, NEC [3669]
		IRS NUMBER:				770015491
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1031

	BUSINESS ADDRESS:	
		STREET 1:		400 WEST CALIFORNIA AVENUE
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94086
		BUSINESS PHONE:		4087491888

	MAIL ADDRESS:	
		STREET 1:		400 W CALIFORNIA
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94086
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-09-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000741696</issuerCik>
        <issuerName>APPLIED SIGNAL TECHNOLOGY INC</issuerName>
        <issuerTradingSymbol>APSG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001250007</rptOwnerCik>
            <rptOwnerName>WONG KENWAY</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>400 W. CALIFORNIA AVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUNNYVALE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94086</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP Wireless Comm Syst Div.</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2005-09-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>41781</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2005-09-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>36181</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Options vested in installments of 20% per year for five (5) years, beginning on the anniversary date of November 20, 1997, with an expiration date of November 20, 2005.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Kenway Wong</signatureName>
        <signatureDate>2005-09-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----