THIRD ALLONGE
                                       TO
                          SECURED NOTE (COMMERCIAL) OF
                             GRC INTERNATIONAL, INC.
                                       TO
                     MERCANTILE-SAFE DEPOSIT & TRUST COMPANY
                           IN THE PRINCIPAL AMOUNT OF
              TWO MILLION TWO HUNDRED THOUSAND DOLLARS ($2,200.000)
                             DATED February 12, 1996

                                   WITNESSETH:

By consent of the Maker,  as evidenced by its  execution of this Third  Allonge,
the Secured Note  (Commercial)  identified  in the caption  above (the  "Secured
Note") is hereby  amended as follows  (unless  otherwise  defined or the context
otherwise  requires,  the defined terms used herein shall have the same meanings
assigned to them in the Secured Note):

          1.   The reference to "September 1, 1997" in the first sentence of the
               Secured Note,  revised in the First  Allonge dated  September 24,
               1996  to  "September  1,  1998",  and in the  Second  Allonge  to
               "September 1, 1999", shall be changed to September 1, 2000.

          2.   All other terms and  conditions  of the Secured Note shall remain
               the same.  This Third  Allonge shall not be deemed a novation nor
               shall  it  limit,   reduce  or   otherwise   affect  the  Maker's
               obligations  set forth in the Secured Note. This Third Allonge is
               made in  addition  to, and not in  substitution  of, the  Maker's
               original obligations as described in the Secured Note. This Third
               Allonge  shall be affixed to the original  Secured Note and shall
               be considered to be a part thereof.

This Third Allonge,  executed under seal in Baltimore,  Maryland and intended to
be a sealed instrument, is dated August 4, 1998 and is effective as of September
1, 1998.


ATTEST/WITNESS:                  GRC INTERNATIONAL, INC.



/s/ Michele L. Zeck              By:     /s/ Ronald B. Alexander
-------------------                      ---------------------------------------
                                 Name:   Ronald B. Alexander
                                 Title:  Treasurer and Chief Financial Officer


<PAGE>



                                  THIRD ALLONGE
                                       TO
                          SECURED NOTE (COMMERCIAL) OF
                             GRC INTERNATIONAL, INC.
                                       TO
                     MERCANTILE-SAFE DEPOSIT & TRUST COWANY
                           IN THE PRINCIPAL AMOUNT OF
                    FOUR HUNDRED THOUSAND DOLLARS ($400,000)
                               DATED March 8, 1996

                                   WITNESSETH:

By consent of the Maker,  as evidenced by its  execution of this Third  Allonge,
the Secured Note  (Commercial)  identified  in the caption  above (the  "Secured
Note") is hereby  amended as follows  (unless  otherwise  defined or the context
otherwise  requires,  the defined terms used herein shall have the same meanings
assigned to them in the Secured Note):

          1.   The  reference to  "September  1, 1997" in the first se ntence of
               the Secured Note,  revised in the First  Allonge dated  September
               24, 1996 to  "September  1, 1998",  and in the Second  Allonge to
               "September 1, 1999", shall be changed to September 1, 2000.

          2. The principal amount of the Note shall be decreased to $150,000.

          3.   All other terms and  conditions  of the Secured Note shall remain
               the same.  This Third  Allonge shall not be deemed a novation nor
               shall  it  limit,   reduce  or   otherwise   affect  the  Maker's
               obligations  set forth in the Secured Note. This Third Allonge is
               made in  addition  to, and not in  substitution  of, the  Maker's
               original obligations as described in the Secured Note. This Third
               Allonge  shall be affixed to the original  Secured Note and shall
               be considered to be a part thereof.

This Third Allonge,  executed under seal in Baltimore,  Maryland and intended to
be a sealed instrument, is dated August 4, 1998 and is effective as of September
1, 1998.

ATTEST/WITNESS:                    GRC INTERNATIONAL, INC.


/s/ Michele L. Zeck                By:     /s/ Ronald B. Alexander
-------------------                        -------------------------------------
                                   Name:   Ronald B. Alexander
                                   Title:  Treasurer and Chief Financial Officer


<PAGE>



                                  THIRD ALLONGE
                                       TO
                          SECURED NOTE (COMMERCIAL) OF
                             GRC INTERNATIONAL, INC.
                                       TO
                    NIERCANTILE-SAFE DEPOSIT & TRUST CONVANY
                           IN THE PRINCIPAL AMOUNT OF
              TWO MILLION SIX HUNDRED THOUSAND DOLLARS ($2,600,000)
                               DATED June 7, 1996

                                   WITNESSETH:

By consent of the Maker,  as evidenced by its  execution of this Third  Allonge,
the Secured Note  (Commercial)  identified  in the caption  above (the  "Secured
Note") is hereby  amended as follows  (unless  otherwise  defined or the context
otherwise  requires,  the defined terms used herein shall have the same meanings
assigned to them in the Secured Note):

          1.   The reference to "September 1, 1997" in the first sentence of the
               Secured Note,  revised in the First  Allonge dated  September 24,
               1996  to  "September  1,  1998",  and in the  Second  Allonge  to
               "September 1, 1999", shall be changed to September 1, 2000.

          2.   All other terms and  conditions  of the Secured Note shall remain
               the same.  This Third  Allonge shall not be deemed a novation nor
               shall  it  limit,   reduce  or   otherwise   affect  the  Maker's
               obligations  set forth in the Secured Note. This Third Allonge is
               made in  addition  to, and not in  substitution  of, the  Maker's
               original obligations as described in the Secured Note. This Third
               Allonge  shall be affixed to the original  Secured Note and shall
               be considered to be a part thereof.

This Third Allonge,  executed under seal in Baltimore,  Maryland and intended to
be a sealed instrument, is dated August 4, 1998 and is effective as of September
1, 1998.

ATTEST/WITNESS:                   GRC INTERNATIONAL, INC.


/s/ Michele L. Zeck               By:     /s/ Ronald B. Alexander
-------------------                       --------------------------------------
                                  Name:   Ronald B. Alexander
                                  Title:  Treasurer and Chief Financial Officer