PARKER CHAPIN FLATTAU & KL;IMPL, LLP
                                  [LETTERHEAD]

                                  May 12, 1998


Xybernaut Corporation
12701 Fair Lakes Circle
Fairfax, Virginia 22033

Gentlemen:

            We have  acted as  counsel  to  Xybernaut  Corporation,  a  Delaware
corporation  (the "Company"),  in connection with the Registration  Statement on
Form S-3 (the  "Registration  Statement")  being filed with the  Securities  and
Exchange  Commission  under the Securities Act of 1933, as amended,  relating to
the offering of 2,340,938  shares (the "Shares") of Common Stock, par value $.01
per share (the "Common Stock") of the Company.

            Capitalized  terms  used  herein  and not  defined  shall  have  the
meanings given to them in the Registration Statement.

            In connection  with the  foregoing,  we have  examined  originals or
copies,  satisfactory to us, of the Company's (i) Certificate of  Incorporation,
(ii) By-laws and (iii) resolutions of the Company's board of directors.  We have
also  reviewed  such other  matters of law and examined and relied upon all such
corporate  records,  agreements,  certificates  and other  documents  as we have
deemed relevant and necessary as a basis for the opinion hereinafter  expressed.
In such  examination,  we have assumed the  genuineness of all  signatures,  the
authenticity  of all documents  submitted to us as originals and the  conformity
with the  original  documents  of all  documents  submitted  to us as  copies or
facsimiles.  As to any facts  material to such  opinion,  we have, to the extent
that  relevant  facts  were  not  independently  established  by us,  relied  on
certificates  of  public   officials  and  certificates  of  officers  or  other
representatives of the Company.

            Based upon and subject to the foregoing,  we are of the opinion that
the Shares,  when issued  pursuant  to the terms and  conditions  of the Private
Equity Line Credit  Agreement,  Warrant A, Warrant B and the Put Options will be
validly issued, fully paid and non-assessable.








Xybernaut Corporation
Exhibit 5.1 Opinion to Registration Statement on Form S-3


            We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                                              Very truly yours,


                                         /S/ PARKER CHAPIN FLATTAU & KLIMPL, LLP
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                                             PARKER CHAPIN FLATTAU & KLIMPL, LLP