INTERNAL REVENUE SERVICE                        DEPARTMENT OF THE TREASURY
P.O. BOX 2508
CINCINNATI, OH  45201

                                        Employer Identification Number:
Date:    Jan 7, 2000                     22-1852179
                                        DLN:
MANTECH INTERNATIONAL CORP               17007265006019
C/O STEVE D. KITTRELL                   Person to Contact:
MCGUIRE WOODS BATTLE & BOOTHE LLP        JOEL HOBBS             ID# 52002
1050 CONNECTICUT AVE NW STE 1200        Contact Telephone Number:
WASHINGTON, DC  20036                    (877) 829-5500
                                        Plan Name:
                                         MANTECH INTERNATIONAL
                                         401K PLAN
                                        Plan Number: 002


Dear Applicant:

        We have made a favorable determination on your plan, identified above,
based on the information supplied. Please keep this letter in your permanent
records.

        Continued qualification of the plan under its present form will depend
on its effect in operation. (See section 1.401-1(b)(3) of the Income Tax
Regulations.) We will review the status of the plan in operation periodically.

        The enclosed document explains the significance of this favorable
determination letter, points out some events that may affect the qualified
status of your employee retirement plan, and provides information on the
reporting requirements for your plan. It also describes some events that
automatically nullify it. It is very important that you read the publication.

        This letter relates only to the status of your plan under the Internal
Revenue Code. It is not a determination regarding the effect of other federal or
local statutes.

        This determination is subject to your adoption of the proposed
amendments submitted in your letter dated 12/16/99. The proposed amendments
should be adopted on or before the date prescribed by the regulations under Code
section 401(b).

        This determination letter is applicable for the amendment(s) executed on
12/29/98.

        This plan has been madatorily disaggregated, permissively aggregated, or
restructured to satisfy the nondiscrimination requirements.

        This plan satisfies the nondiscrimination in amount requirement of
section 1.401(a)(4)-1(b)(2) of the regulations on the basis of a design-based
safe harbor described in the regulations.

        This plan satisfies the nondiscriminatory current availability
requirements of section 1.401(a)(4)-4(b) of the regulations with respect to
those benefits, rights and features that are currently available to all
employees in the plan's coverage group. For this purpose, the plan's coverage
group consists of those employees treated as currently benefitting for purposes
of

                                                              Letter 835 (DO/CG)

                                       11


                                      -2-

MANTECH INTERNATIONAL CORP


demonstrating that the plan satisfies the minimum coverage requirements of
section 410(b) of the Code.

       This letter considers the changes in the qualifications requirements
made by the Uruguay Round Agreements Act (GATT), Pub. L. 103-465, and the
Taxpayer Relief Act of 1997, Pub. L. 105-34, and the changes in the
qualifications requirements made by the Small Business Job Protection Act of
1996, Pub. L. 104-188, that are effective before the first day of the first
plan year beginning after December 31, 1998.

       The information on the enclosed Publication 794 is an integral part of
this determination. Please be sure to read and keep it with this letter.

       The requirement for employee benefits plans to file summary plan
descriptions (SPD) with the U.S. Department of Labor was eliminated
effective August 5, 1997. For more details, call 1-800-998-7542 for a free copy
of the SPD card.

       We have sent a copy of this letter to your representative as indicated
in the power of attorney.

       If you have questions concerning this matter, please contact the person
whose name and telephone number are shown above.


                                             Sincerely yours,


                                             /s/ Carol D. Gold

                                             Carol D. Gold
                                             Director, Employee Plans


Enclosures:
Publication 794






                                                              Letter 835 (DO/CG)

                                       12