-----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,
 EditEcVH6gGthwY1M2Ttanu0+adF+4OQrr/OOmy9UHTRorVJVBHg1VAhzMb/MFgT
 63Ik8/h0Qa2GHaBjBLG4Jw==

<SEC-DOCUMENT>0001140361-05-004072.txt : 20050611
<SEC-HEADER>0001140361-05-004072.hdr.sgml : 20050611
<ACCEPTANCE-DATETIME>20050527124211
ACCESSION NUMBER:		0001140361-05-004072
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050526
FILED AS OF DATE:		20050527
DATE AS OF CHANGE:		20050527

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Comen Thomas Casey
		CENTRAL INDEX KEY:			0001293815

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32396
		FILM NUMBER:		05862614

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		802-269-2000

	MAIL ADDRESS:	
		STREET 1:		5601 WEST BUCKEYE ROAD
		CITY:			PHOENIX
		STATE:			AZ
		ZIP:			86043

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			KNIGHT TRANSPORTATION INC
		CENTRAL INDEX KEY:			0000929452
		STANDARD INDUSTRIAL CLASSIFICATION:	TRUCKING (NO LOCAL) [4213]
		IRS NUMBER:				860649974
		STATE OF INCORPORATION:			AZ
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		5601 W BUCKEYE RD
		CITY:			PHOENIX
		STATE:			AZ
		ZIP:			85043
		BUSINESS PHONE:		6022692000

	MAIL ADDRESS:	
		STREET 1:		5601 W BUCKEYE RD
		CITY:			PHOENIX
		STATE:			AZ
		ZIP:			85043
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 3
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2005-05-26</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000929452</issuerCik>
        <issuerName>KNIGHT TRANSPORTATION INC</issuerName>
        <issuerTradingSymbol>KNX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001293815</rptOwnerCik>
            <rptOwnerName>Comen Thomas Casey</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>5601 WEST BUCKEYE ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PHOENIX</rptOwnerCity>
            <rptOwnerState>AZ</rptOwnerState>
            <rptOwnerZipCode>85043</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>Executive Vice President</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.5467</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2007-03-01</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-02-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>37500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>23.30</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-05-16</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-05-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This option will vest in five equal annual installments on March 1, 2007, 2008, 2009, 2010, and 2011.</footnote>
        <footnote id="F2">This option will vest in five equal annual installments on May 16, 2008, 2009, 2010, 2011, and 2012.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Casey Comen</signatureName>
        <signatureDate>2005-05-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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