<SUBMISSION>
<ACCESSION-NUMBER>0001183755-08-000002
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20080521
<FILING-DATE>20080522
<DATE-OF-FILING-DATE-CHANGE>20080522
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>KRATOS DEFENSE & SECURITY SOLUTIONS, INC.
<CIK>0001069258
<ASSIGNED-SIC>4899
<IRS-NUMBER>133818604
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1228
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>4810 EASTGATE MALL
<STREET2>.
<CITY>SAN DIEGO
<STATE>CA
<ZIP>92121
<PHONE>858-812-7300
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>4810 EASTGATE MALL
<STREET2>.
<CITY>SAN DIEGO
<STATE>CA
<ZIP>92121
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>WIRELESS FACILITIES INC
<DATE-CHANGED>19990817
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>CARANO BANDEL L
<CIK>0001183755
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-27231
<FILM-NUMBER>08853523
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>525 UNIVERSITY AVENUE
<STREET2>SUITE 1300
<CITY>PALO ALTO
<STATE>CA
<ZIP>94301
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-05-21</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001069258</issuerCik>
        <issuerName>KRATOS DEFENSE &amp; SECURITY SOLUTIONS, INC.</issuerName>
        <issuerTradingSymbol>KTOS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001183755</rptOwnerCik>
            <rptOwnerName>CARANO BANDEL L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAK INVESTMENT PARTNERS</rptOwnerStreet1>
            <rptOwnerStreet2>ONE GORHAM ISLAND</rptOwnerStreet2>
            <rptOwnerCity>WESTPORT</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06880</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Director Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.80</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-05-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3056</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2008-05-21</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2018-05-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3056</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3056</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents options received in lieu of cash fees from Mr. Carano's service on the Issuer's Board of Directors as approved by the Board of Directors on May 21, 2008.  The grant is effective May 21, 2008.</footnote>
        <footnote id="F2">The Director Options became fully exercisable on the date of the grant.</footnote>
        <footnote id="F3">Not applicable</footnote>
        <footnote id="F4">Includes Director Option to purchase 3,008 shares of Common Stock, which is held by Mr. Carano on behalf of Oak Investment Partners X, Limited Partnership (&quot;Oak X, L.P.&quot;); and Director Option to purchase 48 shares of Common Stock, which is held by Mr. Carano on behalf of Oak X Affiliates Fund, Limited Partnership (&quot;Oak X Affiliates, L.P.&quot;).  Mr. Carano is a Managing Member of Oak Associates X, L.L.C., the General Partner of Oak X, L.P. and a Managing Member of Oak X Affiliates, L.L.C., the General Partner of Oak X Affiliates, L.P.</footnote>
    </footnotes>

    <remarks>Remarks

Bandel L. Carano is a Director of Wireless Facilities, Inc..  Mr. Carano is a Managing Member of Oak Associates X, L.L.C., the General Partner of Oak X, L.P.; and a Managing Member of Oak X Affiliates, L.L.C., the General Partner of Oak X Affiliates, L.P.

Oak X, L.P. and Oak X Affiliates, L.P. are not reporting persons on this Form 4 because they are no longer subject to Section 16, as they are no longer 10% owners

Each Reporting Person disclaims the existence of a &quot;group&quot; and disclaims beneficial ownership of any securities (except to the extent of such Reporting Person's pecuniary interest in such securities) other than any securities reported herein as being directly owned by such Reporting Person, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of any such securities for purposes of Section 16 or for any other purpose.</remarks>

    <ownerSignature>
        <signatureName>Bandel L. Carano</signatureName>
        <signatureDate>2008-05-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
