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THESE SECURITIES AND THE SECURITIES ISSUABLE UPON THEIR EXERCISE HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933 AND MAY NOT BE TRANSFERRED UNLESS
COVERED BY AN EFFECTIVE REGISTRATION STATEMENT UNDER SAID ACT, A "NO ACTION"
LETTER FROM THE SECURITIES AND EXCHANGE COMMISSION WITH RESPECT TO SUCH
TRANSFER, A TRANSFER MEETING THE REQUIREMENTS OF RULE 144 OF THE SECURITIES AND
EXCHANGE COMMISSION, OR AN OPINION OF COUNSEL SATISFACTORY TO THE ISSUER TO THE
EFFECT THAT ANY SUCH TRANSFER IS EXEMPT FROM SUCH REGISTRATION.

                             XYBERNAUT CORPORATION

                         COMMON STOCK PURCHASE WARRANT

         1.       Issuance. In consideration of good and valuable
consideration, the receipt of which is hereby acknowledged by Xybernaut
Corporation, a Delaware corporation (the "Company"), Crystalite Investments
Ltd., or registered assigns (the "Holder") is hereby granted the right to
purchase at any time until 5:00 P.M., New York City time, on October 1, 2004
(the "Expiration Date"), Five Hundred Thousand (500,000) fully paid and
nonassessable shares of the Company's Common Stock, par value $.01 per share
(the "Common Stock") at an initial exercise price of $1.01 per share (the
"Exercise Price"), subject to further adjustment as set forth in Section 6
hereof.

         2.       Exercise of Warrants. This Warrant is exercisable in whole or
in part at the Exercise Price per share of Common Stock payable hereunder,
payable in cash or by certified or official bank check, or by "cashless
exercise", by means of tendering this Warrant Certificate to the Company to
receive a number of shares of Common Stock equal in Market Value to the
difference between the Market Value of the shares of Common Stock issuable upon
exercise of this Warrant and the total cash exercise price thereof. Upon
surrender of this Warrant Certificate with the annexed Notice of Exercise Form
duly executed, together with payment of the Exercise Price for the shares of
Common Stock purchased, the Holder shall be entitled to receive a certificate
or certificates for the shares of Common Stock so purchased. For the purposes
of this Section 2, "Market Value" shall be an amount equal to the average
closing bid price of a share of Common Stock for the ten (10) days preceding
the Company's receipt of the Notice of Exercise Form duly executed multiplied
by the number of shares of Common Stock to be issued upon surrender of this
Warrant Certificate.

         3.       Reservation of Shares. The Company hereby agrees that at all
times during the term of this Warrant there shall be reserved for issuance upon
exercise of this Warrant such number of shares of its Common Stock as shall be
required for issuance upon exercise of this Warrant (the "Warrant Shares").

         4.       Mutilation or Loss of Warrant. Upon receipt by the Company of
evidence satisfactory to it of the loss, theft, destruction or mutilation of
this Warrant, and (in the case of

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loss, theft or destruction) receipt of reasonably satisfactory indemnification,
and (in the case of mutilation) upon surrender and cancellation of this
Warrant, the Company will execute and deliver a new Warrant of like tenor and
date and any such lost, stolen, destroyed or mutilated Warrant shall thereupon
become void.

         5.       Rights of the Holder. The Holder shall not, by virtue hereof,
be entitled to any rights of a stockholder in the Company, either at law or
equity, and the rights of the Holder are limited to those expressed in this
Warrant and are not enforceable against the Company except to the extent set
forth herein.

         6.       Protection Against Dilution.

                  6.1      Adjustment Mechanism. If an adjustment of the
Exercise Price is required pursuant to this Section 6, the Holder shall be
entitled to purchase such number of additional shares of Common Stock as will
cause (i) the total number of shares of Common Stock Holder is entitled to
purchase pursuant to this Warrant, multiplied by (ii) the adjusted purchase
price per share, to equal (iii) the dollar amount of the total number of shares
of Common Stock Holder is entitled to purchase before adjustment multiplied by
the total purchase price before adjustment.

                  6.2      Capital Adjustments. In case of any stock split or
reverse stock split, stock dividend, reclassification of the Common Stock,
recapitalization, merger or consolidation, or like capital adjustment affecting
the Common Stock of the Company, the provisions of this Section 6 shall be
applied as if such capital adjustment event had occurred immediately prior to
the date of this Warrant and the original purchase price had been fairly
allocated to the stock resulting from such capital adjustment; and in other
respects the provisions of this Section shall be applied in a fair, equitable
and reasonable manner so as to give effect, as nearly as may be, to the
purposes hereof. A rights offering to stockholders shall be deemed a stock
dividend to the extent of the bargain purchase element of the rights.

         7.       Transfer to Comply with the Securities Act; Registration
Rights.

         (a) This Warrant has not been registered under the Securities Act of
1933, as amended, (the "Act") and has been issued to the Holder for investment
and not with a view to the distribution of either the Warrant or the Warrant
Shares. Neither this Warrant nor any of the Warrant Shares or any other
security issued or issuable upon exercise of this Warrant may be sold,
transferred, pledged or hypothecated in the absence of an effective
registration statement under the Act relating to such security or an opinion of
counsel satisfactory to the Company that registration is not required under the
Act. Each certificate for the Warrant, the Warrant Shares and any other
security issued or issuable upon exercise of this Warrant shall contain a
legend on

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the face thereof, in form and substance satisfactory to counsel for the
Company, setting forth the restrictions on transfer contained in this Section.

         (b) The Company hereby grants to the Holder piggyback registration
rights with respect to the Warrant Shares. In the event the Company is filing a
Registration Statement for itself or on behalf of any of its shareholders, the
Company shall notify the Holder in writing reasonably in advance of such filing
(but at least five business days) and give the Holder the opportunity to
include all or any party of the Warrant Shares (whether or not previously
issued, to the extent permissible under the Act or any regulation promulgated
thereunder. Upon the Holder's notification that the Holder desires to have all
or any portion of the Warrant Shares included in such registration, the Company
shall, at no cost or expense to the Holder, include or cause to be included in
such registration statement the Warrant Shares so identified by the Holder.

         (c) In addition to the registration rights referred to in the
preceding provisions of Section (b), effective after the expiration of the
effectiveness of the Registration Statement as contemplated by the Registration
Rights Agreement, the Holder shall have demand piggy-back registration rights
with respect to the Warrant Shares then held by the Holder or then subject to
issuance upon exercise of this Warrant (collectively, the "Remaining Warrant
Shares"), subject to the conditions set forth below. If, at any time after the
Registration Statement has ceased to be effective, the Company participates
(whether voluntarily or by reason of an obligation to a third party) in the
registration of any shares of the Company's stock, the Company shall give
written notice thereof to the Holder and the Holder shall have the right,
exercisable within ten (10) business days after receipt of such notice, to
demand inclusion of all or a portion of the Holder's Remaining Warrant Shares
in such registration statement.

         8.       Notices. Any notice or other communication required or
permitted hereunder shall be in writing and shall be delivered personally,
telegraphed, telexed, sent by facsimile transmission or sent by certified,
registered or express mail, postage pre-paid. Any such notice shall be deemed
given when so delivered personally, telegraphed, telexed or sent by facsimile
transmission, or, if mailed, two days after the date of deposit in the United
States mails, as follows:

                  (i)      if the to Company, to:

                           Xybernaut Corporation
                           12701 Fair Lakes Circle
                           Suite 550
                           Fairfax, Virginia 22033
                           Fax no.:703-631-6734
                           Attn: Chief Financial Officer

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                  (ii)     if to the Holder, to:
                           Crystalit Investments, Ltd.
                           111 Arlosorov Street
                           Tel Aviv, Israel
                           Fax no.: 011-972-3-691-0476


Any party may be notice given in accordance with this Section to the other
parties designate another address or person for receipt of notices hereunder.

         9.       Supplements and Amendments; Whole Agreement. This Warrant may
be amended or supplemented only by an instrument in writing signed by the
parties hereto. This Warrant of even date herewith contain the full
understanding of the parties hereto with respect to the subject matter hereof
and thereof and there are no representations, warranties, agreements or
understandings other than expressly contained herein and therein.

         10.      Governing Law. This Warrant shall be deemed to be a contract
made under the laws of the State of New York and for all purposes shall be
governed by and construed in accordance with the laws of such State applicable
to contracts to be made and performed entirely within such State.

         11.      Counterparts.  This Warrant may be executed in any number of
counterparts and each of such counterparts shall for all purposes be deemed to
be an original, and all such counterparts shall together constitute but one and
the same instrument.

         12.      Descriptive Headings.  Descriptive headings of the several
Sections of this Warrant are inserted for convenience only and shall not
control or affect the meaning or construction of any of the provisions hereof.

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     IN WITNESS WHEREOF, the parties hereto have executed this Warrant as of
the __th day of December 1999.

                                             XYBERNAUT CORPORATION

                                             By:
                                                 --------------------------
                                                      Name: Steve A. Newman
                                                      Title: Vice Chairman

Attest:

-----------------------------

-----------------------------
Chief Administrative Officer

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                                    FORM OF
                         NOTICE OF EXERCISE OF WARRANT

     The undersigned hereby irrevocably elects to exercise the right,
represented by the Warrant Certificate dated as of __________, 1999, to
purchase __________ shares of the Common Stock, par value $.01 per share, of
Xybernaut Corporation and tenders herewith payment in accordance with Section 1
of said Common Stock Purchase Warrant.

     Please deliver the stock certificate to:

Dated:

                                             CRYSTALITE INVESTMENTS LTD.

                                             By:
                                                 --------------------------



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