As filed with the Securities and Exchange Commission on January 9, 1998
                                                Registration No. 333-17739
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                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549
                         --------------------------
            
                       POST-EFFECTIVE AMENDMENT NO. 1
                                  TO FORM S-3
                            REGISTRATION STATEMENT
                                    UNDER
                         THE SECURITIES ACT OF 1933
                         --------------------------

                         COMPUTER DATA SYSTEMS, INC.
            (Exact name of registrant as specified in its charter)

          Maryland                                      52-0882982
(State or other jurisdiction of                      (I.R.S. employer
 incorporation or organization)                    identification number)

                               One Curie Court
                          Rockville, Maryland 20850
                               (301) 921-7000
   (Address, including zip code, and telephone number, including area code,
                 of registrant's principal executive offices)

                               Bradley W. Kopp
                            Chief Financial Officer
                            Computer Data Systems, Inc.
                               One Curie Court
                          Rockville, Maryland 20850
                               (301) 921-7000
           (Name, address, including zip code, and telephone number,
                  including area code, of agent for service)

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                          EXPLANATORY STATEMENT
                          ---------------------

      On December 16, 1997, Computer Data Systems, Inc. ("CDSI") and
Affiliated Computer Services, Inc. ("ACS") consummated the merger of ACS
Acquisition Corp. with and into CDSI (the "Merger") on the terms and
conditions more fully described in Registration Statement No. 333-40351 on
Form S-4 filed by ACS on November 17, 1997.  As a result of the closing of the
Merger, the shares previously registered by CDSI for possible sale by
InTuition, Inc. were converted into shares of ACS Class A Common Stock in
accordance with the 1.759 exchange ratio specified in the Agreement and Plan
of Merger.  Pursuant to CDSI's undertaking in the Registration Statement, CDSI
files this Post-Effective Amendment No. 1 to remove from registration the
shares of CDSI Common Stock registered thereunder.

                                 SIGNATURES
                                 ----------

      Pursuant to the requirements of the Securities Act of 1933, the
registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-3 and has duly caused this
Post-Effective Amendment No. 1 to Registration Statement No. 333-17739 to be
signed on its behalf by the undersigned, thereunto duly authorized, in
Rockville, Maryland, on the date indicated.

                         COMPUTER DATA SYSTEMS, INC.

Date: January 9, 1998         By: /s/ Peter A. Bracken
                                 ------------------------- 
                                 Peter A. Bracken
                                 Chief Executive Officer and President

      Pursuant to the requirements of the Securities Act of 1933, this
Post-Effective Amendment No. 1 to Registration Statement No. 333-17739 has been
signed below by the following persons in the capacities and on the date
indicated.

   Signature                   Title                        Date
   ---------                   -----                        ----

/s/ Peter A. Bracken       President and Chief Executive    January 9, 1998
- --------------------       Officer (Principal Executive 
Peter A. Bracken           Officer)

/s/ Bradley W. Kopp        Chief Financial Officer          January 9, 1998
- --------------------       (Principal Financial and 
Bradley W. Kopp             Accounting Officer)

/s/ Jeffrey A. Rich        Chairman of the Board of         January 9, 1998
- --------------------       Directors
Jeffrey A. Rich

/s/ Henry G. Hortenstine   Director                         January 9, 1998
- ------------------------          
Henry G. Hortenstine

/s/ David W. Black         Director                         January 9, 1998
- ---------------------
David W. Black