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                                                                   Exhibit 10.19

                                                                  EXECUTION COPY

                        AMENDMENT NO. 3 dated as of June 30, 200O (this
                  "Amendment"), to the Credit Agreement dated as of June 23,
                  1999, as amended by Amendment No. 1 dated as of January
                  13, 200O (the "Credit Agreement"), among ANTEON CORPORATION, a
                  Virginia corporation (the "Borrower"), the Lenders (as defined
                  in Article I of the Credit Agreement), CREDIT SUISSE FIRST
                  BOSTON, a bank organized under the laws of Switzerland, acting
                  through its New York branch, as an Issuing Bank (as defined in
                  Article I of the Credit Agreement), and as administrative
                  agent (in such capacity, the "Administrative Agent") for the
                  Lenders, MELLON BANK, N.A., a national banking association, as
                  syndication agent (in such capacity, the "Syndication Agent"),
                  as swingline lender (in such capacity, the "Swingline
                  Lender"), and as collateral agent (in such capacity, the
                  "Collateral Agent") for the Lenders, and DEUTSCHE BANK AG, New
                  York Branch, as documentation agent (in such capacity, the
                  "Documentation Agent").

      A. Pursuant to the Credit Agreement, the Lenders and the Issuing Banks
have extended, and have agreed to extend, credit to the Borrower.

      B. The Borrower has requested that the Required Lenders agree to amend the
Credit Agreement as provided herein. The Required Lenders are willing so to
amend the Credit Agreement pursuant to the terms and subject to the conditions
set forth herein.

      C. Capitalized terms used but not defined herein shall have the meanings
assigned to them in the Credit Agreement.

      Accordingly, in consideration of the mutual agreements herein contained
and other good and valuable consideration, the sufficiency and receipt of which
are hereby acknowledged, the parties hereto agree as follows:

      SECTION 1. Amendment to Section 1.01. The definition of "EBITDA" set forth
in Section 1.O1 of the Credit Agreement is hereby amended by deleting the words
"and (e)" set forth therein and substituting therefor the following:

      "(e) during any period of four consecutive fiscal quarters ending on or
      prior to September 30, 2000, severance costs associated with the Merger in
      an aggregate amount not to exceed $1,860,000, and (f)"

      SECTION 2. Representations and Warranties. To induce the other parties
hereto to enter into this Amendment, the Borrower represents and warrants to
each of the Lenders, the Administrative Agent, the Issuing Banks, the Collateral
Agent and the Documentation Agents that, after giving effect to this Amendment,
(a) the representations and warranties set forth in Article III of the Credit
Agreement are true and correct in all material respects on and as of the date
hereof, except to the extent such representations and warranties expressly
relate to an earlier date, and (b) no Default or Event of Default has occurred
and is continuing.

      SECTION 3. Effectiveness. This Amendment shall become effective as of the
date first written above on the date on which the Administrative Agent shall
have received


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counterparts of this Amendment that, when taken together, bear the signatures of
the Borrower, the Guarantors and the Required Lenders.

      SECTION 4. Effect of Amendment. Except as expressly set forth herein, this
Amendment shall not by implication or otherwise limit, impair, constitute a
waiver of, or otherwise affect the rights and remedies of the Lenders, the
Issuing Banks, the Collateral Agent, the Administrative Agent, the Syndication
Agent or the Documentation Agent under the Credit Agreement or any other Loan
Document, and shall not alter, modify, amend or in any way affect any of the
terms, conditions, obligations, covenants or agreements contained in the Credit
Agreement or any other Loan Document, all of which are ratified and affirmed in
all respects and shall continue in full force and effect. Nothing herein shall
be deemed to entitle any Loan Party to a consent to, or a waiver, amendment,
modification or other change of, any of the terms, conditions, obligations,
covenants or agreements contained in the Credit Agreement or any other Loan
Document in similar or different circumstances. This Amendment shall apply and
be effective only with respect to the provisions of the Credit Agreement
specifically referred to herein. After the date hereof, any reference to the
Credit Agreement shall mean the Credit Agreement, as modified hereby. This
Amendment shall constitute a "Loan Document" for all purposes of the Credit
Agreement and the other Loan Documents.

      SECTION 5. Counterparts. This Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed and delivered shall be deemed an original, but all such
counterparts together shall constitute but one and the same contract. Delivery
of an executed counterpart of a signature page of this Amendment by facsimile
transmission shall be as effective as delivery of a manually executed
counterpart hereof.

      SECTION 6. Applicable Law. THIS AMENDMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

      SECTION 7. Headings. The headings of this Amendment are for purposes of
reference only and shall not limit or otherwise affect the meaning hereof.

      SECTION 8. Expenses. The Borrower agrees to reimburse the Administrative
Agent for all out-of-pocket expenses in connection with this Amendment,
including the reasonable fees, charges and disbursements of Cravath, Swaine &
Moore, counsel for the Administrative Agent.

      SECTION 9. Acknowledgment of Guarantors. Each of the Guarantors hereby
acknowledges receipt and notice of, and consents to the terms of, this
Amendment.


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            TN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed by their duly authorized officers, all as of the date and year
first above written.

                              ANTEON CORPORATION,

                              by:
                                 /s/    Carlton B. Crenshaw
                                 -----------------------------------------------
                                 Name:  Carlton B. Crenshaw
                                 Title: Senior Vice President Finance and
                                        Administration


                              ANALYSIS & TECHNOLOGY, INC.,

                              by:
                                 /s/    Carlton B. Crenshaw
                                 -----------------------------------------------
                                 Name:  Carlton B. Crenshaw
                                 Title: Vice President


                              INTERACTIVE MEDIA CORP.,

                              by:
                                 /s/    Carlton B. Crenshaw
                                 -----------------------------------------------
                                 Name:  Carlton B. Crenshaw
                                 Title: Vice President


                              TECHMATICS, INC.,

                              by:
                                 /s/    Carlton B. Crenshaw
                                 -----------------------------------------------
                                 Name:  Carlton B. Crenshaw
                                 Title: Treasurer


                              VECTOR DATA SYSTEMS, INC.,

                              by:
                                 /s/    Carlton B. Crenshaw
                                 -----------------------------------------------
                                 Name:  Carlton B. Crenshaw
                                 Title: Treasurer

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                              CREDIT SUISSE FIRST BOSTON, individually
                              and as Administrative Agent and Issuing Bank,

                              by:
                                 /s/    Robert Hetu
                                 -----------------------------------------------
                                 Name:  Robert Hetu
                                 Title: Vice President

                              by:
                                 /s/    Thomas G. Muoio
                                 -----------------------------------------------
                                 Name:  Thomas G. Muoio
                                 Title: Vice President


                              MELLON BANK, N.A., individually and as
                              Collateral Agent, Swingline Lender and Syndication
                              Agent,

                              by:
                                 /s/    David A. Reed
                                 -----------------------------------------------
                                 Name:  David A. Reed
                                 Title: First Vice President


                              DEUTSCHE BANK AG, New York Branch. as
                              Documentation Agent.

                              by:
                                 /s/    Robert Wood
                                 -----------------------------------------------
                                 Name:  Robert Wood
                                 Title: Director

                              by:/s/    John L. Quinn
                                 -----------------------------------------------
                                 Name:  John L. Quinn
                                 Title: Assistant Vice President


                              DEUTSCHE BANK AG, New York and/or Cayman
                              Islands Branches, as Lender,

                              by:
                                 /s/    Robert Wood
                                 -----------------------------------------------
                                 Name:  Robert Wood
                                 Title: Director

                              by:
                                 /s/    John L. Quinn
                                 -----------------------------------------------
                                 Name:  John L. Quinn
                                 Title: Assistant Vice President


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                              THE BANK OF NOVA SCOTIA,

                              by:
                                 /s/    J.W. Campbell
                                 -----------------------------------------------
                                 Name:  J.W. Campbell
                                 Title: Managing Director


                              BANK POLSKA KASA OPIEKI S.A.,

                              by:
                                 /s/    Hussein B. El-Tawil
                                 -----------------------------------------------
                                 Name:  Hussein B. El-Tawil
                                 Title: Vice President


                              BRANCH BANKING & TRUST COMPANY,

                              by:
                                 /s/    William A. Nalls
                                 -----------------------------------------------
                                 Name:  William A. Nalls
                                 Title: Senior Vice President


                              FLEET NATIONAL BANK,

                              by:
                                 /s/    Roger C. Boucher
                                 -----------------------------------------------
                                 Name:  Roger C. Boucher
                                 Title: Senior Vice President


                              IBM CREDIT CORPORATION,

                              by:
                                 /s/    Thomas S. Carcio
                                 -----------------------------------------------
                                 Name:  Thomas S. Carcio
                                 Title: Manager of Credit, Commercial &
                                        Specialty Financing


                              PNC BANK,

                              by:
                                 /s/    Daniel J. Paull
                                 -----------------------------------------------
                                 Name:  Daniel J. Paull
                                 Title: Vice President


                              TRANSAMERICA BUSINESS CREDIT CORPORATION,

                              by:
                                 /s/    Perry Vavoules
                                 -----------------------------------------------
                                 Name:  Perry Vavoules
                                 Title: Senior Vice President