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                                                                 Exhibit (a)(4)

                           Offer to Purchase for Cash

                     All Outstanding Shares of Common Stock

                                       of

                            GRC INTERNATIONAL, INC.

                                       at

                              $15.00 NET PER SHARE

                                       by

                                LMN CORPORATION

                          a wholly owned subsidiary of

                                   AT&T CORP.

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, EASTERN TIME, ON
MONDAY, MARCH 20, 2000, UNLESS THE OFFER IS EXTENDED.

                                                               February 22, 2000

To Brokers, Dealers, Commercial Banks,
  Trust Companies and Other Nominees:

     We have been appointed by LMN Corporation, a Delaware corporation (the
"Purchaser") and a wholly owned subsidiary of AT&T Corp., a New York corporation
("Parent"), to act as Dealer Manager in connection with the Purchaser's offer to
purchase all outstanding shares of Common Stock, par value $.10 per share (the
"Shares"), of GRC International, Inc., a Delaware corporation (the "Company"),
at a purchase price of $15.00 per Share, net to the seller in cash, without
interest thereon, upon the terms and subject to the conditions set forth in the
Offer to Purchase dated February 22, 2000 (the "Offer to Purchase") and in the
related Letter of Transmittal (which, as amended or supplemented from time to
time, collectively constitute the "Offer") enclosed herewith.

     Please furnish copies of the enclosed materials to those of your clients
for whose accounts you hold Shares registered in your name or in the name of
your nominee.

     The Offer is conditioned upon, among other things, (i) there being validly
tendered and not properly withdrawn prior to the expiration of the Offer at
least a majority of the total number of outstanding Shares on a fully diluted
basis on the date of purchase and (ii) the expiration or termination of any
applicable waiting periods under the Hart-Scott-Rodino Antitrust Improvements
Act of 1976, as amended. The Offer is also subject to the other conditions set
forth in the Offer to Purchase. See Section 14 of the Offer to Purchase.

     THE BOARD OF DIRECTORS OF THE COMPANY HAS UNANIMOUSLY APPROVED THE OFFER,
THE MERGER (AS DEFINED BELOW) AND THE MERGER AGREEMENT (AS DEFINED BELOW) AND
DETERMINED THAT THE TERMS OF EACH ARE ADVISABLE, FAIR TO, AND IN THE BEST
INTERESTS OF, THE COMPANY AND ITS STOCKHOLDERS, AND RECOMMENDS THAT THE
COMPANY'S STOCKHOLDERS ACCEPT THE OFFER AND TENDER THEIR SHARES PURSUANT TO THE
OFFER.

     The Offer is being made pursuant to an Agreement and Plan of Merger, dated
as of February 14, 2000 (the "Merger Agreement"), among the Company, Parent and
the Purchaser pursuant to which, following the consummation of the Offer and in
accordance with the Delaware General Corporation Law, and subject to the
satisfaction or waiver of certain conditions, the Purchaser will be merged with
and into the Company (the "Merger"), with the Company continuing as the
surviving corporation and as a wholly owned subsidiary of Parent.
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     Enclosed herewith for your information and forwarding to your clients are
copies of the following documents:

          1.  The Offer to Purchase dated February 22, 2000.

          2.  The Letter of Transmittal for your use to tender Shares and for
     the information of your clients. Facsimile copies of the Letter of
     Transmittal may be used to tender Shares.

          3.  A printed form of letter which may be sent to your clients for
     whose accounts you hold Shares registered in your name or in the name of
     your nominee, with space provided for obtaining such clients' instructions
     with regard to the Offer.

          4.  The Notice of Guaranteed Delivery for Shares to be used to accept
     the Offer if certificates for Shares ("Share Certificates") and all other
     required documents are not immediately available or cannot be delivered to
     EquiServe (the "Depositary") by the Expiration Date (as defined in the
     Offer to Purchase) or if the procedure for book-entry transfer cannot be
     completed by the Expiration Date.

          5.  A letter to stockholders from Joseph R. Wright, Jr., the Chairman
     of the Board of Directors of the Company accompanied by the Company's
     Solicitation/Recommendation Statement on Schedule 14D-9.

          6.  Guidelines of the Internal Revenue Service for Certification of
     Taxpayer Identification Number on Substitute Form W-9.

          7.  A return envelope addressed to the Depositary.

     YOUR PROMPT ACTION IS REQUESTED.  WE URGE YOU TO CONTACT YOUR CLIENTS AS
PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL
EXPIRE AT 12:00 MIDNIGHT, EASTERN TIME, ON MONDAY, MARCH 20, 2000, UNLESS THE
OFFER IS EXTENDED.

     In order to accept the Offer, a duly executed and properly completed Letter
of Transmittal and any required signature guarantees, or an Agent's Message (as
defined in the Offer to Purchase) in connection with a book-entry delivery of
Shares, and any other required documents should be sent to the Depositary and
either Share Certificates representing the tendered Shares should be delivered
to the Depositary, or Shares should be tendered by book-entry transfer into the
Depositary's account maintained at the Book Entry Transfer Facility (as
described in the Offer to Purchase), all in accordance with the instructions set
forth in the Letter of Transmittal and the Offer to Purchase.

     If holders of Shares wish to tender, but it is impracticable for them to
forward their Share Certificates or other required documents on or prior to the
Expiration Date or to comply with the book-entry transfer procedures on a timely
basis, a tender may be effected by following the guaranteed delivery procedures
specified in Section 3 of the Offer to Purchase.

     The Purchaser will not pay any commissions or fees to any broker, dealer or
other person (other than the Information Agent) for soliciting tenders of Shares
pursuant to the Offer. The Purchaser will, however, upon request, reimburse you
for customary clerical and mailing expenses incurred by you in forwarding any of
the enclosed materials to your clients. The Purchaser will pay or cause to be
paid any stock transfer taxes applicable to its purchase of Shares pursuant to
the Offer, except as otherwise provided in Instruction 6 of the Letter of
Transmittal.

     Any inquiries you may have with respect to the Offer should be addressed
to, and additional copies of the enclosed material may be obtained from, the
Information Agent or the Dealer Manager at their respective addresses and
telephone numbers set forth on the back cover of the Offer to Purchase.

                                             Very truly yours,

                                             LEHMAN BROTHERS

     NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU
OR ANY OTHER PERSON THE AGENT OF PARENT, THE PURCHASER, THE COMPANY, THE DEALER
MANAGER, THE DEPOSITARY OR THE INFORMATION AGENT, OR ANY AFFILIATE OF ANY OF
THEM, OR AUTHORIZE YOU OR ANY OTHER PERSON TO MAKE ANY STATEMENT OR USE ANY
DOCUMENT ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE OFFER OTHER THAN THE
ENCLOSED DOCUMENTS AND THE STATEMENTS CONTAINED THEREIN.