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                                                                      EXHIBIT 5

                                 March 31, 2000

American Management Systems, Incorporated
4050 Legato Road
Fairfax, Virginia 22033

     Ladies and Gentlemen:

     We have acted as counsel to American Management Systems, Incorporated (the
"Company"), a Delaware corporation, in connection with the registration of
20,000 shares (the "Shares") of Common Stock, $0.01 par value per share, of the
Company pursuant to a Registration Statement on Form S-8 under the Securities
Act of 1933, as amended (the "Registration Statement") relating to the Company's
1999 Contractor Stock Option Plan (the "Plan").

     Based upon examination and review of (i) the Second Restated Certificate of
Incorporation of the Company, as amended, (ii) the Bylaws of the Company, as
amended, (iii) the resolutions of the Board of Directors of the Company dated
December 3, 1999, and (iv) the Plan, we are of the opinion that the Shares have
been duly authorized for issuance by the Company, and that upon issuance and
delivery in accordance with the Plan referred to in the Registration Statement,
the Shares will be validly issued, fully paid and nonassessable.

     Our opinions stated in this letter are based on the published compilations
of the General Corporation Law of the State of Delaware, applicable provisions
of the Delaware Constitution and the reported judicial decisions interpreting
each, in effect on the date of this letter.  The opinions expressed in this
letter are limited to the matters set forth herein, and no other opinions should
be inferred beyond the matters expressly stated.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                                              Very truly yours,


                                                               /s/ SHAW PITTMAN

                                                                   SHAW PITTMAN

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