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EXHIBIT 10.1

                            OPNET TECHNOLOGIES, INC.

                        2000 Employee Stock Purchase Plan
                           (Amended October 22, 2002)

     1.   Purpose. The purpose of this 2000 Employee Stock Purchase Plan (the
"Plan") of the Company is to provide eligible employees of the Company and
certain of its subsidiaries with opportunities to purchase shares of the
Company's common stock, par value $0.001 per share (the "Common Stock"). Three
hundred thousand (300,000) shares of Common Stock in the aggregate have been
approved for this purpose. This Plan is intended to qualify as an "employee
stock purchase plan" as defined in Section 423 of the Internal Revenue Code of
1986, as amended (the "Code"), and the regulations promulgated thereunder, and
shall be interpreted consistent therewith.

     2.   Administration. The Plan will be administered by the Company's Board
of Directors (the "Board") or by a Committee appointed by the Board (the
"Committee"). The Board or the Committee has authority to make rules and
regulations for the administration of the Plan and its interpretation and
decisions with regard thereto shall be final and conclusive.

     3.   Eligibility. All employees of the Company, including members of the
Board of Directors who are employees, and all employees of any subsidiary of the
Company (as defined in Section 424(f) of the Code) designated by the Board or
the Committee from time to time (a "Designated Subsidiary"), are eligible to
participate in any one or more of the offerings of Options (as defined in
Section 9) to purchase Common Stock under the Plan provided that:

          (a)  they are customarily employed by the Company or a Designated
     Subsidiary for more than 20 hours a week and for at least three months in a
     calendar year; and

          (b)  they have been employed by the Company or a Designated Subsidiary
     for at least three months prior to enrolling in the Plan; and

          (c)  they are employees of the Company or a Designated Subsidiary on
     the first day of the applicable Plan Period (as defined below).

     No employee may be granted an option hereunder if such employee,
immediately after the option is granted, owns 5% or more of the total combined
voting power or value of the stock of the Company or any subsidiary. For
purposes of the preceding sentence, the attribution rules of Section 424(d) of
the Code shall apply in determining the stock ownership of an employee, and all
stock which the employee has a contractual right to purchase shall be treated as
stock owned by the employee.

     4.   Offerings. The Company will make one or more offerings ("Offerings")
to employees to purchase stock under this Plan. Offerings will begin each
January 1 and July 1, or the first business day thereafter (the "Offering
Commencement Dates"). Each Offering Commencement Date will begin a six-month
period (a "Plan Period") during which payroll deductions will be made and held
for the purchase of Common Stock at the end of the Plan Period. The Board or the
Committee may, at its discretion, choose a different Plan Period of 12 months or
less for subsequent Offerings. Notwithstanding anything to the contrary, the
first Plan Period shall begin on the first day of the first fiscal quarter
beginning after the closing of a firm commitment, registered initial public
offering by the Company or, if later, the date that the Company has filed with
the United States Securities and Exchange Commission an effective Registration
Statement on Form S-8 for purposes of registering under the Securities Act of
1933, as amended, all shares of Common Stock issuable under this Plan, and shall
end on the June 30 or December 31 first thereafter occurring.

     5.   Participation. An employee eligible on the Offering Commencement Date
of any Offering may participate in such Offering by completing and forwarding a
payroll deduction authorization form to the employee's

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appropriate payroll office at least 15 days prior to the applicable Offering
Commencement Date. The form will authorize a regular payroll deduction from the
Compensation received by the employee during the Plan Period. Unless an employee
files a new form or withdraws from the Plan, his or her deductions and purchases
will continue at the same rate for future Offerings under the Plan as long as
the Plan remains in effect. The term "Compensation" means the amount of money
reportable on the employee's Federal Income Tax Withholding Statement, excluding
overtime, shift premium, incentive or bonus awards, allowances and
reimbursements for expenses such as relocation allowances for travel expenses,
income or gains on the exercise of Company stock options or stock appreciation
rights, and similar items, whether or not shown on the employee's Federal Income
Tax Withholding Statement, but including, in the case of salespersons, sales
commissions to the extent determined by the Board or the Committee.

     6.   Deductions. The Company will maintain payroll deduction accounts for
all participating employees. With respect to any Offering made under this Plan,
an employee may authorize a payroll deduction in any dollar amount up to a
maximum of 10% of the Compensation he or she receives during the Plan Period or
such shorter period during which deductions from payroll are made. Payroll
deductions may be at any percentage (up to 10%) of Compensation, with any change
in Compensation during the Plan Period to result in an automatic corresponding
change in the dollar amount withheld. The minimum payroll deduction is such
percentage of Compensation as may be established from time to time by the Board
or the Committee.

     No employee may be granted an Option (as defined in Section 9) which
permits his or her rights to purchase Common Stock under this Plan and any other
employee stock purchase plan (as defined in Section 423(b) of the Code) of the
Company and its subsidiaries, to accrue at a rate which exceeds $25,000 of the
fair market value of such Common Stock (determined at the Offering Commencement
Date of the Plan Period) for each calendar year in which the Option is
outstanding at any time.

     7.   Deduction Changes. An employee may decrease or discontinue his or her
payroll deduction once during any Plan Period, by filing a new payroll deduction
authorization form. However, an employee may not increase his or her payroll
deduction during a Plan Period. If an employee elects to discontinue his or her
payroll deductions during a Plan Period, but does not elect to withdraw his or
her funds pursuant to Section 8 hereof, funds deducted prior to his or her
election to discontinue will be applied to the purchase of Common Stock on the
Exercise Date (as defined below).

     8.   Interest. Interest will not be paid on any employee accounts, except
to the extent that the Board or the Committee, in its sole discretion, elects to
credit employee accounts with interest at such per annum rate as it may from
time to time determine.

     9.   Withdrawal of Funds. An employee may at any time prior to the close of
business on the last business day in a Plan Period and for any reason
permanently draw out the balance accumulated in the employee's account and
thereby withdraw from participation in an Offering. Partial withdrawals are not
permitted. The employee may not begin participation again during the remainder
of the Plan Period. The employee may participate in any subsequent Offering in
accordance with terms and conditions established by the Board or the Committee.

     10.  Purchase of Shares. On the Offering Commencement Date of each Plan
Period, the Company will grant to each eligible employee who is then a
participant in the Plan an option ("Option") to purchase on the last business
day of such Plan Period (the "Exercise Date"), at the Option Price hereinafter
provided for, the largest number of whole shares of Common Stock of the Company
as does not exceed the number of shares determined by multiplying $2,083 by the
number of full months in the Offering Period and dividing the result by the
closing price (as defined below) on the Offering Commencement Date of such Plan
Period.

     The purchase price for each share purchased will be 85% of the closing
price of the Common Stock on (i) the first business day of such Plan Period or
(ii) the Exercise Date, whichever closing price is less. Such closing price
shall be (a) the closing price on any national securities exchange on which the
Common Stock is listed, (b) the closing price of the Common Stock on the Nasdaq
National Market or (c) the average of the closing bid and asked prices in the
over-the-counter-market, whichever is applicable, as published in The Wall
Street Journal. If no sales

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of Common Stock were made on such a day, the price of the Common Stock for
purposes of clauses (a) and (b) above shall be the reported price for the next
preceding day on which sales were made.

     Each employee who continues to be a participant in the Plan on the Exercise
Date shall be deemed to have exercised his or her Option at the Option Price on
such date and shall be deemed to have purchased from the Company the number of
full shares of Common Stock reserved for the purpose of the Plan that his or her
accumulated payroll deductions on such date will pay for, but not in excess of
the maximum number determined in the manner set forth above.

     Any balance remaining in an employee's payroll deduction account at the end
of a Plan Period will be automatically refunded to the employee, except that any
balance which is less than the purchase price of one share of Common Stock will
be carried forward into the employee's payroll deduction account for the
following Offering, unless the employee elects not to participate in the
following Offering under the Plan, in which case the balance in the employee's
account shall be refunded.

     11.  Issuance of Certificates. Certificates representing shares of Common
Stock purchased under the Plan may be issued only in the name of the employee,
in the name of the employee and another person of legal age as joint tenants
with rights of survivorship, or (in the Company's sole discretion) in the name
of a brokerage firm, bank or other nominee holder designated by the employee.
The Company may, in its sole discretion and in compliance with applicable laws,
authorize the use of book entry registration of shares in lieu of issuing stock
certificates.

     12.  Rights on Retirement, Death or Termination of Employment. In the event
of a participating employee's termination of employment prior to the last
business day of a Plan Period, no payroll deduction shall be taken from any pay
due and owing to an employee and the balance in the employee's account shall be
paid to the employee or, in the event of the employee's death, (a) to a
beneficiary previously designated in a revocable notice signed by the employee
(with any spousal consent required under state law) or (b) in the absence of
such a designated beneficiary, to the executor or administrator of the
employee's estate, or (c) if no such executor or administrator has been
appointed to the knowledge of the Company, to such other person(s) as the
Company may, in its discretion, designate. If, prior to the last business day of
the Plan Period, the Designated Subsidiary by which an employee is employed
shall cease to be a subsidiary of the Company, or if the employee is transferred
to a subsidiary of the Company that is not a Designated Subsidiary, the employee
shall be deemed to have terminated employment for the purposes of this Plan.

     13.  Optionees Not Stockholders. Neither the granting of an Option to an
employee nor the deductions from his or her pay shall constitute such employee a
stockholder of the shares of Common Stock covered by an Option under this Plan
until such shares have been purchased by and issued to him.

     14.  Rights Not Transferable. Rights under this Plan are not transferable
by a participating employee other than by will or the laws of descent and
distribution, and are exercisable during the employee's lifetime only by the
employee.

     15.  Application of Funds. All funds received or held by the Company under
this Plan may be combined with other corporate funds and may be used for any
corporate purpose.

     16.  Adjustment in Case of Changes Affecting Common Stock. In the event of
a subdivision of outstanding shares of Common Stock or the payment of a dividend
in Common Stock, the number of shares approved for this Plan, and the share
limitation set forth in Section 9, shall be increased proportionately, and such
other adjustment shall be made as may be deemed equitable by the Board or the
Committee. In the event of any other change affecting the Common Stock, such
adjustment shall be made as may be deemed equitable by the Board or the
Committee to give proper effect to such event.

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     17.  Merger. If the Company shall at any time merge or consolidate with
another corporation and the holders of the capital stock of the Company
immediately prior to such merger or consolidation continue to hold at least 80%
by voting power of the capital stock of the surviving corporation ("Continuity
of Control"), the holder of each Option then outstanding will thereafter be
entitled to receive at the next Exercise Date upon the exercise of such Option
for each share as to which such Option shall be exercised the securities or
property which a holder of one share of the Common Stock was entitled to upon
and at the time of such merger or consolidation, and the Board or the Committee
shall take such steps in connection with such merger or consolidation as the
Board or the Committee shall deem necessary to assure that the provisions of
Section 15 shall thereafter be applicable, as nearly as reasonably may be, in
relation to the said securities or property as to which such holder of such
Option might thereafter be entitled to receive thereunder.

     In the event of a merger or consolidation of the Company with or into
another corporation which does not involve Continuity of Control, or of a sale
of all or substantially all of the assets of the Company while unexercised
Options remain outstanding under the Plan, (a) subject to the provisions of
clauses (b) and (c), after the effective date of such transaction, each holder
of an outstanding Option shall be entitled, upon exercise of such Option, to
receive in lieu of shares of Common Stock, shares of such stock or other
securities as the holders of shares of Common Stock received pursuant to the
terms of such transaction; or (b) all outstanding Options may be cancelled by
the Board or the Committee as of a date prior to the effective date of any such
transaction and all payroll deductions shall be paid out to the participating
employees; or (c) all outstanding Options may be cancelled by the Board or the
Committee as of the effective date of any such transaction, provided that notice
of such cancellation shall be given to each holder of an Option, and each holder
of an Option shall have the right to exercise such Option in full based on
payroll deductions then credited to his or her account as of a date determined
by the Board or the Committee, which date shall not be less than ten (10) days
preceding the effective date of such transaction.

     18.  Amendment of the Plan. The Board may at any time, and from time to
time, amend this Plan in any respect, except that (a) if the approval of any
such amendment by the shareholders of the Company is required by Section 423 of
the Code, such amendment shall not be effected without such approval, and (b) in
no event may any amendment be made which would cause the Plan to fail to comply
with Section 423 of the Code.

     19.  Insufficient Shares. In the event that the total number of shares of
Common Stock specified in elections to be purchased under any Offering plus the
number of shares purchased under previous Offerings under this Plan exceeds the
maximum number of shares issuable under this Plan, the Board or the Committee
will allot the shares then available on a pro rata basis.

     20.  Termination of the Plan. This Plan may be terminated at any time by
the Board. Upon termination of this Plan all amounts in the accounts of
participating employees shall be promptly refunded.

     21.  Governmental Regulations. The Company's obligation to sell and deliver
Common Stock under this Plan is subject to listing on a national stock exchange
or quotation on the Nasdaq National Market (to the extent the Common Stock is
then so listed or quoted) and the approval of all governmental authorities
required in connection with the authorization, issuance or sale of such stock.

     22.  Governing Law. The Plan shall be governed by Delaware law except to
the extent that such law is preempted by federal law.

     23.  Issuance of Shares. Shares may be issued upon exercise of an Option
from authorized but unissued Common Stock, from shares held in the treasury of
the Company, or from any other proper source.

     24.  Notification upon Sale of Shares. Each employee agrees, by entering
the Plan, to promptly give the Company notice of any disposition of shares
purchased under the Plan where such disposition occurs within two years after
the date of grant of the Option pursuant to which such shares were purchased.

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     25.  Effective Date and Approval of Shareholders. The Plan shall take
effect on March 13, 2000 subject to approval by the shareholders of the Company
as required by Section 423 of the Code, which approval must occur within twelve
months of the adoption of the Plan by the Board.


     Adopted by the Board of Directors of
     the Company on March 13, 2000.

     Approved by the stockholders of the
     Company on June 30, 2000.

     Amended by the Board of Directors of the
     Company on October 22, 2002.

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