EXHIBIT 4.10

                              XYBERNAUT CORPORATION
                             12701 FAIR LAKES CIRCLE
                                    SUITE 550
                             FAIRFAX, VIRGINIA 22033


                                                January 1, 2002

IBS Technologies LLC
301 Park Avenue
New York, New York 10022
Attn:  Mr. Ben Cohen

Gentlemen:

     Reference is made to that certain Marketing and Showcase  Agreement,  dated
as of January 1, 2002 (the "Agreement"),  by and between IBS Technologies LLC, a
New York limited liability company and  successor-in-interest to NWCS, LLC d/b/a
International Business Solutions ("IBS"), and Xybernaut Corporation,  a Delaware
corporation ("Xybernaut"). Pursuant to the terms of the Agreement and subject to
all of the terms and conditions  contained therein, IBS has agreed to provide to
Xybernaut  certain  marketing  services,   including,   without  limitation,  an
allocation  of certain  leased  showroom  space for the  display of  Xybernaut's
products and solutions.

     As partial  consideration for the services provided  Xybernaut  pursuant to
the Agreement,  Xybernaut  agrees to issue to IBS 400,000 shares of common stock
of  Xybernaut  (the  "Shares")  and to  register  the  Shares on a  registration
statement on Form S-3 (the "Registration Statement").  Xybernaut further agrees,
at its cost and expense, to prepare and file the Registration Statement covering
the Shares with the Securities and Exchange  Commission and use its best efforts
to effect the  registration  of the Shares under the  Securities Act of 1933, as
amended (the "Act"). IBS shall cooperate with Xybernaut as reasonably  requested
by Xybernaut in connection with the  preparation and filing of the  Registration
Statement and any supplemented prospectus and/or amended registration statement.

     The Shares are being  offered to IBS in reliance on specific  provisions of
federal and state  securities  laws and  Xybernaut is relying upon the truth and
accuracy of the representations,  warranties, acknowledgments and understandings
of IBS  set  forth  herein  for  purposes  of  qualifying  for  exemptions  from
registration under the Act and applicable state securities laws.

     The  Shares  have not been  registered  under the Act or any state or other
securities  laws and have been issued to IBS for  investment and not with a view
to the distribution of the Shares. Except as set forth above, Xybernaut is under
no  obligation  to register  the Shares  under the Act or any  applicable  state
securities  laws  or to  take  any  action  to  make  any  exemption  from  such
registration  provisions  available.  The  Shares  may  not  be  offered,  sold,
transferred,  pledged, encumbered,  hypothecated or otherwise disposed of in the
absence of an effective  registration  statement  under the Act relating to such
Shares or an opinion,  which shall be in form, scope and substance  satisfactory
to  Xybernaut,  of  counsel  (who  shall  be  satisfactory  to  Xybernaut)  that



registration  is not  required  under the Act or under any  applicable  state or
other securities  laws. Each  certificate  evidencing the Shares shall contain a
legend on the face thereof,  in form and substance  satisfactory  to counsel for
Xybernaut, setting forth the restrictions on transfer contained herein.

     In connection  with issuance of the Shares,  IBS represents and warrants as
follows:

     (i) IBS is aware of what constitutes,  and fully understands the definition
of,  an  "Accredited  Investor,"  as  that  term  is  defined  in  Regulation  D
promulgated  under the Act and  under  the laws of each  state of which IBS is a
resident,  and is an "Accredited  Investor" for purpose of said Regulation D and
the laws of each state in which IBS is a resident;

     (ii) IBS recognizes that an investment in Xybernaut  involves a high degree
of risk;  and IBS is capable of evaluating the risks and merits of an investment
in the Shares by virtue of its  experience  as an  investor  and its  knowledge,
experience,  and  sophistication  in financial  and business  matters and IBS is
capable of bearing the entire loss of its investment in the Shares;

     (iii) IBS is and will be acquiring  the Shares for IBS's own  account,  and
not with a view to any  resale or  distribution  of the  Shares,  in whole or in
part,  in violation  of the Act or any  applicable  securities  laws and has not
offered or sold any of the Shares and has no present  intention  or agreement to
divide the Shares with others for purposes of selling, offering, distributing or
otherwise disposing of any of the Shares; and

     (iv) In making its  decision to acquire the Shares,  IBS has relied  solely
upon its independent  investigation and due diligence  regarding the business of
Xybernaut  and  an  investment  in  the  Shares  and is  not  relying  upon  any
representations   or  warranties  made  by  or  on  behalf  of  Xybernaut.   IBS
acknowledges  that it has had an  opportunity  to consult  with its own attorney
regarding legal matters concerning Xybernaut and an investment in the Shares and
to consult with its tax advisor  regarding the tax consequences of acquiring the
Shares.

     This letter agreement shall be governed by and construed in accordance with
the laws of the  State of New  York,  without  regard  to its  conflicts  of law
principles. This letter agreement may not be modified, waived or amended, except
by an instrument in writing executed by each of IBS and Xybernaut. If there is a
conflict or inconsistency  between the terms and provisions of the Agreement and
this letter agreement, the Agreement shall govern and be controlling.

     Please confirm your  concurrence  and agreement with respect to the subject
matter  hereof,  by executing  and  returning  the enclosed  copy of this letter
agreement to the undersigned.

                                        Very truly yours,

                                        XYBERNAUT CORPORATION


                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:

AGREED AND ACCEPTED:

IBS TECHNOLOGIES LLC


By:
   -------------------------
   Name:
   Title: