FIRST MODIFICATION AND EXTENSION AGREEMENT



       THIS FIRST MODIFICATION AND EXTENSION AGREEMENT (this
"Agreement"), effective as of the 12th day of April 2000, is by
and among UNITED BANK, a Virginia banking corporation (the
"Bank"); HADRON, INC., a New York corporation, AVENUE
TECHNOLOGIES, INC., a Virginia corporation, VAIL RESEARCH AND
TECHNOLOGY CORPORATION, a Virginia corporation, SYCOM SERVICES,
INC., a Delaware corporation, and ENGINEERING & INFORMATION
SERVICES, INC., a Virginia corporation (hereinafter individually
and collectively called the "Borrower"); and C.W. GILLULY, MARTHA
ALICE GILLULY and JON M. STOUT (the "Guarantors").

                        WITNESSETH THAT:

       WHEREAS, the Bank is the owner and holder of that certain
Revolving Commercial Note dated June 29, 1999, made by the
Borrower and payable to the order of the Bank, in the original
principal amount of One Million Five Hundred Thousand and no/100
Dollars ($1,500,000.00) and bearing interest and being payable in
accordance with the terms and conditions therein set forth (the
"Note"); and

       WHEREAS, the Note is secured by, and issued pursuant to
the terms of, a certain Loan and Security Agreement dated June
29, 1999, between the Borrower and the Bank (as amended, the
"Loan Agreement"); and

       WHEREAS, as of the effective date hereof, the principal
balance of the Note is $1,076,616.21 and the parties hereto
desire to extend the maturity date of the Note and to modify the
terms thereof and of the Loan Agreement.

       NOW, THEREFORE, for Ten Dollars ($10.00) and other good
and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, the parties hereto agree as follows:

       1.   The maturity date of the Note is hereby extended to
October 31, 2000.

       2.   The definition of "Date of Maturity" in the Note and
the Loan Agreement is hereby changed to "October 31, 2000".

       3.   Contemporaneously with the execution and delivery of
this Agreement, Hadron, Inc., a Borrower, and C.W. Gilluly, one
of the Guarantors, shall execute and deliver to the Bank a
subordination agreement subordinating payment of a certain
$430,000 Note dated February 15, 2000, made by Hadron, Inc. to
the order of C.W. Gilluly, the outstanding principal balance on
the date hereof being $230,000.000, upon terms satisfactory to
the Bank.

       4.   The Borrower and the Guarantors hereby acknowledge
and agree that, as of the effective date hereof, the unpaid
principal balance of the Note is $1,076,616.21 and that there are
no set-offs or defenses against the Note or the Loan Agreement.

       5.   The Guarantors join in this Agreement for the purpose
of signifying their consent hereto and acknowledge and agree that
there are no set-offs or defenses against their guaranties and
that their guaranties of the Note shall apply to the Note as
extended hereby.

       6.   The parties to this Agreement do not intend that this
Agreement be construed as a novation of the Note or the Loan
Agreement.

       7.   Except as hereby expressly extended and modified, the
Note and Loan Agreement shall otherwise be unchanged, shall
remain in full force and effect, and are hereby expressly
approved, ratified and confirmed.  A legend shall be placed on
the face of the Note indicating that its terms have been modified
hereby, and the original of this Agreement shall be affixed to
the original of the Note.

       8.   This Agreement shall be governed in all respects by
the laws of the Commonwealth of Virginia and shall be binding
upon and shall inure to the benefit of the parties hereto and
their respective heirs, executors, administrators, personal
representatives, successors and assigns.

WITNESS the following signatures and seals.

                              HADRON, INC.
[SEAL]

                                    /S/ C.W. GILLULY
                              By:  -----------------------
                                   Name:  C.W. Gilluly
                                   Title:  Chairman

                              AVENUE TECHNOLOGIES, INC.          [SEAL]


                                   /S/ S. AMBER GORDON
                              By: -------------------------
                                   Name: S. AMBER GORDON
                                   Title: Corporate Secretary

                              VAIL RESEARCH AND TECHNOLOGY
                               CORPORATION                       [SEAL]

                                  /S/ S. AMBER GORDON
                              By: -------------------------
                                   Name: S. AMBER GORDON
                                   Title: Corporate Secretary
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                              SYCOM SERVICES, INC.               [SEAL]

                                  /S/ S. AMBER GORDON
                              By: ------------------------
                                   Name: S. AMBER GORDON
                                   Title: Corporate Secretary



                              ENGINEERING & INFORMATION SERVICES,
                              INC.                               [SEAL]

                                   /S/ S. AMBER GORDON
                              By:  -----------------------
                                   Name: S. AMBER GORDON
                                   Title: Corporate Secretary


                                   /S/ C.W. GILLULY
                              -----------------------             [SEAL]
                              C.W. GILLULY

                                  /S/ MARTHA ALICE GILLULY
                              -----------------------             [SEAL]
                              MARTHA ALICE GILLULY


                                  /S/ JON M. STOUT
                              -----------------------             [SEAL]
                              JON M. STOUT


                              UNITED BANK                         [SEAL]

                                  /S/ LOUISE M. WAGER
                              By: -----------------------
                                  Louise M. Wager, Vice President

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