-----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,
 J8cV8KOlUk//Vh4SKBUKu2jfeqaiIRg03lwDPcJe+fXij4oOi8IXCfJ7s0zBXNKX
 nVxVdfVya5+DUFmLUdueQg==

<SEC-DOCUMENT>0001209191-06-012304.txt : 20060222
<SEC-HEADER>0001209191-06-012304.hdr.sgml : 20060222
<ACCEPTANCE-DATETIME>20060222141034
ACCESSION NUMBER:		0001209191-06-012304
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060217
FILED AS OF DATE:		20060222
DATE AS OF CHANGE:		20060222

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Banks Roy
		CENTRAL INDEX KEY:			0001305065

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21319
		FILM NUMBER:		06635726

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		1-801-818-3311

	MAIL ADDRESS:	
		STREET 1:		6129 WEST 9600 NORTH
		CITY:			HIGHLAND
		STATE:			UT
		ZIP:			84003

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			LIGHTBRIDGE INC
		CENTRAL INDEX KEY:			0001017172
		STANDARD INDUSTRIAL CLASSIFICATION:	RADIO TELEPHONE COMMUNICATIONS [4812]
		IRS NUMBER:				043065140
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		30 CORPORATE DRIVE
		CITY:			BURLINGTON
		STATE:			MA
		ZIP:			01803
		BUSINESS PHONE:		7813594000

	MAIL ADDRESS:	
		STREET 1:		30 CORPORATE DRIVE
		CITY:			BURLINGTON
		STATE:			MA
		ZIP:			01803
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>doc4a.xml
<DESCRIPTION>FORM 4/A SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2006-02-17</periodOfReport>

    <dateOfOriginalSubmission>2006-02-21</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001017172</issuerCik>
        <issuerName>LIGHTBRIDGE INC</issuerName>
        <issuerTradingSymbol>LTBG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001305065</rptOwnerCik>
            <rptOwnerName>Banks Roy</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6129 WEST 9600 NORTH</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HIGHLAND</rptOwnerCity>
            <rptOwnerState>UT</rptOwnerState>
            <rptOwnerZipCode>84003</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President, Authorize.Net</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Common stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.00</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-02-17</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>0</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2006-02-17</value>
            </exerciseDate>
            <expirationDate>
                <value>2006-02-17</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>n/a</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>200000</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On February 21, 2006, the reporting person mistakenly filed a Form 4 reporting the acquisition of an option to purchase 50,000 shares of common stock, which option grant did not in fact occur.  As of February 21, 2006, the reporting person beneficially owned derivative securities consisting of options to purchase only 200,000 shares of common stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Roy Banks</signatureName>
        <signatureDate>2006-02-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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