Exhibit 5.1

                                            July 15, 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 165,441  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 5%
Convertible  Preferred Stock and Common Stock Purchase Agreement will be validly
issued, fully paid and non-assessable.

           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