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                                                                   EXHIBIT 10.16

                          CONCORD COMMUNICATIONS, INC.

                 2004 NON-EXECUTIVE EMPLOYEE STOCK PURCHASE PLAN

ARTICLE 1 - PURPOSE.

      This 2004 Non-Executive Employee Stock Purchase Plan (the "Plan") is
intended to encourage stock ownership by all eligible employees of CONCORD
COMMUNICATIONS, INC. (the "Company"), a Massachusetts corporation, and its
participating subsidiaries (as defined in Article 17) so that they may share in
the growth of the Company by acquiring or increasing their proprietary interest
in the Company. The Plan is designed to encourage eligible employees to remain
in the employ of the Company and its participating subsidiaries. The Plan is
intended to constitute an "employee stock purchase plan" within the meaning of
Section 423(b) of the Internal Revenue Code of 1986, as amended (the "Code").

ARTICLE 2 - ADMINISTRATION OF THE PLAN.

      The Plan may be administered by the Compensation Committee of the Board of
Directors or a committee appointed by the Board of Directors of the Company (the
"Committee"). The Committee shall consist of not less than two members of the
Company's Board of Directors (the "Board of Directors"). The Board of Directors
may from time to time remove members from, or add members to, the Committee.
Vacancies on the Committee, howsoever caused, shall be filled by the Board of
Directors. The Committee may select one of its members as Chairman, and shall
hold meetings at such times and places as it may determine. Acts by a majority
of the Committee, or acts reduced to or approved in writing by a majority of the
members of the Committee, shall be the valid acts of the Committee.

      The interpretation and construction by the Committee of any provisions of
the Plan or of any option granted under it shall be final, unless otherwise
determined by the Board of Directors. The Committee may from time to time adopt
such rules and regulations for carrying out the Plan as it may deem best,
provided that any such rules and regulations shall be applied on a uniform basis
to all employees under the Plan. No member of the Board of Directors or the
Committee shall be liable for any action or determination made in good faith
with respect to the Plan or any option granted under it.

      In the event the Board of Directors fails to appoint or refrains from
appointing a Committee, the Board of Directors shall have all power and
authority to administer the Plan. In such event, the word "Committee" wherever
used herein shall be deemed to mean the Board of Directors.

ARTICLE 3 - ELIGIBLE EMPLOYEES.

      All employees, (excluding Officers and Directors to the extent described
below), of the Company or any of its participating subsidiaries whose customary
employment is more than 20 hours per week and for more than five months in any
calendar year shall be eligible to receive options under the Plan to purchase
common stock of the Company, and all eligible employees shall have the same
rights and privileges hereunder. Persons who are eligible employees on the

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first business day of any Payment Period (as defined in Article 5) shall receive
their options as of such day. Persons who become eligible employees after any
date on which options are granted under the Plan shall be granted options on the
first day of the next succeeding Payment Period on which options are granted to
eligible employees under the Plan. In no event, however, may an employee be
granted an option if such employee, immediately after the option was granted,
would be treated as owning stock possessing five percent or more of the total
combined voting power or value of all classes of stock of the Company or of any
parent corporation or subsidiary corporation, as the terms "parent corporation"
and "subsidiary corporation" are defined in Section 424(e) and (f) of the Code.
For purposes of determining stock ownership under this paragraph, the rules of
Section 424(d) of the Code shall apply, and stock which the employee may
purchase under outstanding options shall be treated as stock owned by the
employee. Notwithstanding the foregoing, Officers and Directors of the Company
who are "highly compensated employees" (within the meaning of Section 414(q) of
the Code) shall not be eligible employees and shall not be eligible to receive
options under the Plan. For purpose of the Plan, (a) "Officers" shall mean a
person who is an officer of the Company within the meaning of the
interpretations of the National Association of Securities Dealers, Inc. ("NASD")
under Section 4350(i)(1)(a) of the NASD Marketplace Rules and (b) "Director"
shall mean a member of the Board of Directors of the Company.

ARTICLE 4 - STOCK SUBJECT TO THE PLAN.

      The stock subject to the options under the Plan shall be shares of the
Company's authorized but unissued common stock, par value $0.01 per share (the
"Common Stock"), or shares of Common Stock reacquired by the Company, including
shares purchased in the open market. The aggregate number of shares which may be
issued pursuant to the Plan is 500,000, subject to adjustment as provided in
Article 12. If any option granted under the Plan shall expire or terminate for
any reason without having been exercised in full or shall cease for any reason
to be exercisable in whole or in part, the unpurchased shares subject thereto
shall again be available under the Plan.

ARTICLE 5 - PAYMENT PERIOD AND STOCK OPTIONS.

      The first Payment Period during which payroll deductions will be
accumulated under the Plan shall commence on the later to occur of May 1, 2004
and the first day of the first calendar month following effectiveness of the
Form S-8 registration statement filed with the Securities and Exchange
Commission covering the shares to be issued pursuant to the Plan and shall end
on October 31, 2004. For the remainder of the duration of the Plan, Payment
Periods shall consist of the six-month periods commencing on November 1 and May
1, respectively, and ending on April 30 and October 31, respectively, of each
calendar year.

      Twice each year, on the first business day of each Payment Period, the
Company will grant to each eligible employee an option to purchase on the last
day of such Payment Period, at the Option Price hereinafter provided for, a
maximum of 20,000 shares, on condition that such employee remains eligible to
participate in the Plan throughout the remainder of such Payment Period. The
employee shall be entitled to exercise the option so granted only to the extent
of the employee's accumulated payroll deductions on the last day of such Payment
Period. If the


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participant's accumulated payroll deductions on the last day of the Payment
Period would enable the participant to purchase more than 20,000 shares except
for the 20,000-share limitation, the excess of the amount of the accumulated
payroll deductions over the aggregate purchase price of the 20,000 shares shall
be promptly refunded to the participant by the Company, without interest. The
Option Price per share for each Payment Period initially shall be the lesser of
(i) 85% of the average market price of the Common Stock on the first business
day of the Payment Period and (ii) 85% of the average market price of the Common
Stock on the last business day of the Payment Period, in either event rounded up
to the nearest cent. Notwithstanding the foregoing, the Committee may, by giving
written notice to the eligible employees at least 20 days before the first day
of the next succeeding Payment Period, increase or decrease the then prevailing
Option Price for such next succeeding Payment Period and successive Payment
Periods; provided that (x) such written notice shall set forth the revised
Option Price, and (y) the Option Price shall not be less than the lesser of (i)
85% of the average market price of the Common Stock on the first business day of
the Payment Period and (ii) 85% of the average market price of the Common Stock
on the last business day of the Payment Period, in either event rounded up to
the nearest cent. The foregoing limitation on the number of shares subject to
option and the Option Price shall be subject to adjustment as provided in
Article 12.

      For purposes of the Plan, the term "average market price" on any date
means (i) the average (on that date) of the high and low prices of the Common
Stock on the principal national securities exchange on which the Common Stock is
traded, if the Common Stock is then traded on a national securities exchange; or
(ii) the last reported sale price (on that date) of the Common Stock on the
Nasdaq National Market, if the Common Stock is not then traded on a national
securities exchange; or (iii) the average of the closing bid and asked prices
last quoted (on that date) by an established quotation service for
over-the-counter securities, if the Common Stock is not reported on the Nasdaq
National Market; or (iv) if the Common Stock is not publicly traded, the fair
market value of the Common Stock as determined by the Committee after taking
into consideration all factors which it deems appropriate, including, without
limitation, recent sale and offer prices of the Common Stock in private
transactions negotiated at arm's length.

For purposes of the Plan, the term "business day" means a day on which there is
trading on the Nasdaq National Market or the aforementioned national securities
exchange, whichever is applicable pursuant to the preceding paragraph; and if
neither is applicable, a day that is not a Saturday, Sunday or legal holiday in
The Commonwealth of Massachusetts.

      No employee shall be granted an option which permits the employee's right
to purchase stock under the Plan, and under all other Section 423(b) employee
stock purchase plans of the Company and any parent or subsidiary corporations,
to accrue at a rate which exceeds $25,000 of fair market value of such stock
(determined on the date or dates that options on such stock were granted) for
each calendar year in which such option is outstanding at any time. The purpose
of the limitation in the preceding sentence is to comply with Section 423(b)(8)
of the Code. If the participant's accumulated payroll deductions on the last day
of the Payment Period would otherwise enable the participant to purchase Common
Stock in excess of the Section 423(b)(8) limitation described in this paragraph,
the excess of the amount of the accumulated payroll deductions over the
aggregate purchase price of the shares actually purchased shall be promptly
refunded to the participant by the Company, without interest.



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ARTICLE 6 - EXERCISE OF OPTION.

      Each eligible employee who continues to be a participant in the Plan on
the last day of a Payment Period shall be deemed to have exercised his or her
option on such date and shall be deemed to have purchased from the Company such
number of full shares of Common Stock reserved for the purpose of the Plan as
the participant's accumulated payroll deductions on such date will pay for at
the Option Price, subject to the 20,000-share limit of the option and the
Section 423(b)(8) limitation described in Article 5. If the individual is not a
participant on the last day of a Payment Period, then he or she shall not be
entitled to exercise his or her option and the amount of his or her payroll
deduction shall be refundable without interest. Only full shares of Common Stock
may be purchased under the Plan. Unused payroll deductions remaining in a
participant's account at the end of a Payment Period by reason of the inability
to purchase a fractional share shall be carried forward to the next Payment
Period.

ARTICLE 7 - AUTHORIZATION FOR ENTERING THE PLAN.

      An employee may elect to authorize payroll deductions under the Plan by
filling out, signing and delivering to the Company an authorization:

            A. Stating the percentage to be deducted regularly from the
      employee's pay;

            B. Authorizing the purchase of stock for the employee in each
      Payment Period in accordance with the terms of the Plan; and

            C. Specifying the exact name or names in which stock purchased for
      the employee is to be issued as provided under Article 11 hereof.

Such authorization must be received by the Company at least ten days before the
first day of the next succeeding Payment Period and shall take effect only if
the employee is an eligible employee on the first business day of such Payment
Period. Notwithstanding the foregoing, solely for purposes of the first Payment
Period under the Plan, an employee who is an eligible employee on the first
business day of such Payment Period may elect to authorize payroll deductions
under the Plan by filling out, signing, and delivering to the Company the
written authorization described above so that the Company receives such
authorization no later than [April 30, 2004].

      Unless a participant files a new authorization or withdraws from the Plan,
the deductions and purchases under the authorization the participant has on file
under the Plan will continue from one Payment Period to succeeding Payment
Periods as long as the Plan remains in effect.

      The Company will accumulate and hold for each participant's account the
amounts deducted from his or her pay. No interest will be paid on these amounts.

ARTICLE 8 - MAXIMUM AMOUNT OF PAYROLL DEDUCTIONS.

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      An employee may authorize payroll deductions in an amount (expressed as a
whole percentage) not less than one percent (1%) but not more than ten percent
(10%) of the employee's total compensation, including base pay or salary and any
overtime, bonuses or commissions.

ARTICLE 9 - CHANGE IN PAYROLL DEDUCTIONS.

      Deductions may not be increased or decreased during a Payment Period.
However, a participant may withdraw in full from the Plan in which event the
Company will promptly refund (without interest) the entire balance of the
employer's deduction not previously used to purchase stock under the Plan.

ARTICLE 10 - WITHDRAWAL FROM THE PLAN.

      A participant may withdraw from the Plan (in whole but not in part) at any
time prior to the last day of a Payment Period by delivering a withdrawal notice
to the Company.

      To re-enter the Plan, an employee who has previously withdrawn must file a
new authorization at least ten days before the first day of the next Payment
Period in which he or she wishes to participate. The employee's re-entry into
the Plan becomes effective at the beginning of such Payment Period, provided
that he or she is an eligible employee on the first business day of the Payment
Period.

ARTICLE 11 - ISSUANCE OF STOCK.

      Certificates for stock issued to participants shall be delivered as soon
as practicable after each Payment Period by the Company's transfer agent.

      Stock purchased under the Plan shall be issued only in the name of the
participant, or if the participant's authorization so specifies, in the name of
the participant and another person of legal age as joint tenants with rights of
survivorship.

ARTICLE 12 - ADJUSTMENTS.

      Upon the happening of any of the following described events, a
participant's rights under options granted under the Plan shall be adjusted as
hereinafter provided:

            A. In the event that the shares of Common Stock shall be subdivided
      or combined into a greater or smaller number of shares or if, upon a
      reorganization, split-up, liquidation, recapitalization or the like of the
      Company, the shares of Common Stock shall be exchanged for other
      securities of the Company, each participant shall be entitled, subject to
      the conditions herein stated, to purchase such number of shares of Common
      Stock or amount of other securities of the Company as were exchangeable
      for the number of shares of Common Stock that such participant would have
      been entitled to purchase except for such action, and appropriate
      adjustments shall be made in the purchase price per share to reflect such
      subdivision, combination or exchange; and


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            B. In the event the Company shall issue any of its shares as a stock
      dividend upon or with respect to the shares of stock of the class which
      shall at the time be subject to option hereunder, each participant upon
      exercising such an option shall be entitled to receive (for the purchase
      price paid upon such exercise) the shares as to which the participant is
      exercising his or her option and, in addition thereto (at no additional
      cost), such number of shares of the class or classes in which such stock
      dividend or dividends were declared or paid, and such amount of cash in
      lieu of fractional shares, as is equal to the number of shares thereof and
      the amount of cash in lieu of fractional shares, respectively, which the
      participant would have received if the participant had been the holder of
      the shares as to which the participant is exercising his or her option at
      all times between the date of the granting of such option and the date of
      its exercise.

      Upon the happening of any of the foregoing events, the class and aggregate
number of shares set forth in Article 4 hereof which are subject to options
which have been or may be granted under the Plan and the limitations set forth
in the second paragraph of Article 5 shall also be appropriately adjusted to
reflect the events specified in paragraphs A and B above. Notwithstanding the
foregoing, any adjustments made pursuant to paragraphs A or B shall be made only
after the Committee, based on advice of counsel for the Company, determines
whether such adjustments would constitute a "modification" (as that term is
defined in Section 424 of the Code). If the Committee determines that such
adjustments would constitute a modification, it may refrain from making such
adjustments.

      If the Company is to be consolidated with or acquired by another entity in
a merger, a sale of all or substantially all of the Company's assets or
otherwise (an "Acquisition"), the Committee or the board of directors of any
entity assuming the obligations of the Company hereunder (the "Successor Board")
shall, with respect to options then outstanding under the Plan, either (i) make
appropriate provision for the continuation of such options by arranging for the
substitution on an equitable basis for the shares then subject to such options
either (a) the consideration payable with respect to the outstanding shares of
the Common Stock in connection with the Acquisition, (b) shares of stock of the
successor corporation, or a parent or subsidiary of such corporation, or (c)
such other securities as the Successor Board deems appropriate, the fair market
value of which shall not materially exceed the fair market value of the shares
of Common Stock subject to such options immediately preceding the Acquisition;
or (ii) terminate each participant's options in exchange for a cash payment
equal to the excess of (a) the fair market value on the date of the Acquisition,
of the number of shares of Common Stock that the participant's accumulated
payroll deductions as of the date of the Acquisition could purchase, at an
option price determined with reference only to the first business day of the
applicable Payment Period and subject to the 20,000-share, Code Section
423(b)(8) and fractional-share limitations on the amount of stock a participant
would be entitled to purchase, over (b) the result of multiplying such number of
shares by such option price.

      The Committee or Successor Board shall determine the adjustments to be
made under this Article 12, and its determination shall be conclusive.


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ARTICLE 13 - NO TRANSFER OR ASSIGNMENT OF EMPLOYEE'S RIGHTS.

      An option granted under the Plan may not be transferred or assigned to or
availed by, any other person than by will or the laws of descent and
distribution and may be exercised only by the employee during the employee's
lifetime.

ARTICLE 14 - TERMINATION OF EMPLOYEE'S RIGHTS.

      Whenever a participant ceases to be an eligible employee because of
retirement, voluntary or involuntary termination, resignation, layoff,
discharge, death or for any other reason, his or her rights under the Plan shall
immediately terminate, and the Company shall promptly refund, without interest,
the entire balance of his or her payroll deduction account under the Plan.
Notwithstanding the foregoing, eligible employment shall be treated as
continuing intact while a participant is on military leave, sick leave or other
bona fide leave of absence, for up to 90 days, or for so long as the
participant's right to re-employment is guaranteed either by statute or by
contract, if longer than 90 days.

ARTICLE 15 - TERMINATION AND AMENDMENTS TO PLAN.

      The Plan may be terminated at any time by the Company's Board of Directors
but such termination shall not affect options then outstanding under the Plan.
It will terminate in any case when all or substantially all of the unissued
shares of stock reserved for the purposes of the Plan have been purchased. If at
any time shares of stock reserved for the purpose of the Plan remain available
for purchase but not in sufficient number to satisfy all then unfilled purchase
requirements, the available shares shall be apportioned among participants in
proportion to the amount of payroll deductions accumulated on behalf of each
participant that would otherwise be used to purchase stock, and the Plan shall
terminate. Upon such termination, all payroll deductions not used to purchase
stock will be refunded, without interest.

      The Committee or the Board of Directors may from time to time adopt
amendments to the Plan provided that, without the approval of the stockholders
of the Company, no amendment may (i) increase the number of shares that may be
issued under the Plan; (ii) change the class of employees eligible to receive
options under the Plan, if such action would be treated as the adoption of a new
plan for purposes of Section 423(b) of the Code; or (iii) cause Rule 16b-3 under
the Securities Exchange Act of 1934 to become inapplicable to the Plan.

ARTICLE 16 - LIMITS ON SALE OF STOCK PURCHASED UNDER THE PLAN.

      The Plan is intended to provide shares of Common Stock for investment and
not for resale. The Company does not, however, intend to restrict or influence
any employee in the conduct of his or her own affairs. An employee may,
therefore, sell stock purchased under the Plan at any time the employee chooses,
subject to compliance with any applicable federal or state securities laws and
subject to any restrictions imposed under Article 21 to ensure that tax
withholding obligations are satisfied. THE EMPLOYEE ASSUMES THE RISK OF ANY
MARKET FLUCTUATIONS IN THE PRICE OF THE STOCK.


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ARTICLE 17 - PARTICIPATING SUBSIDIARIES.

      The term "participating subsidiary" shall mean any present or future
subsidiary of the Company, as that term is defined in Section 424(f) of the
Code, which is designated from time to time by the Board of Directors to
participate in the Plan. The Board of Directors shall have the power to make
such designation before or after the Plan is approved by the stockholders.

ARTICLE 18 - 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
covered by an option until such shares have been actually purchased by the
employee.

ARTICLE 19 - APPLICATION OF FUNDS.

      The proceeds received by the Company from the sale of Common Stock
pursuant to options granted under the Plan will be used for general corporate
purposes.

ARTICLE 20 - NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION.

      By electing to participate in the Plan, each participant agrees to notify
the Company in writing immediately after the participant transfers Common Stock
acquired under the Plan, if such transfer occurs within two years after the
first business day of the Payment Period in which such Common Stock was
acquired. Each participant further agrees to provide any information about such
a transfer as may be requested by the Company or any subsidiary corporation in
order to assist it in complying with the tax laws. Such dispositions generally
are treated as "disqualifying dispositions" under Sections 421 and 424 of the
Code, which have certain tax consequences to participants and to the Company and
its participating subsidiaries.

ARTICLE 21 - WITHHOLDING OF ADDITIONAL INCOME TAXES.

      By electing to participate in the Plan, each participant acknowledges that
the Company and its participating subsidiaries are required to withhold taxes
with respect to the amounts deducted from the participant's compensation and
accumulated for the benefit of the participant under the Plan, and each
participant agrees that the Company and its participating subsidiaries may
deduct additional amounts from the participant's compensation, when amounts are
added to the participant's account, used to purchase Common Stock or refunded,
in order to satisfy such withholding obligations. Each participant further
acknowledges that when Common Stock is purchased under the Plan the Company and
its participating subsidiaries may be required to withhold taxes with respect to
all or a portion of the difference between the fair market value of the Common
Stock purchased and its purchase price, and each participant agrees that such
taxes may be withheld from compensation otherwise payable to such participant.
It is intended that tax withholding will be accomplished in such a manner that
the full amount of payroll deductions elected by the participant under Article 7
will be used to purchase Common Stock. However, if amounts sufficient to satisfy
applicable tax withholding obligations have not been withheld from compensation
otherwise payable to any participant, then, notwithstanding any other provision
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the Plan, the Company may withhold such taxes from the participant's accumulated
payroll deductions and apply the net amount to the purchase of Common Stock,
unless the participant pays to the Company, prior to the exercise date, an
amount sufficient to satisfy such withholding obligations. Each participant
further acknowledges that the Company and its participating subsidiaries may be
required to withhold taxes in connection with the disposition of stock acquired
under the Plan and agrees that the Company or any participating subsidiary may
take whatever action it considers appropriate to satisfy such withholding
requirements, including deducting from compensation otherwise payable to such
participant an amount sufficient to satisfy such withholding requirements or
conditioning any disposition of Common Stock by the participant upon the payment
to the Company or such subsidiary of an amount sufficient to satisfy such
withholding requirements.

ARTICLE 22 - GOVERNMENTAL REGULATIONS.

      The Company's obligation to sell and deliver shares of Common Stock under
the Plan is subject to the approval of any governmental authority required in
connection with the authorization, issuance or sale of such shares.

      Government regulations may impose reporting or other obligations on the
Company with respect to the Plan. For example, the Company may be required to
identify shares of Common Stock issued under the Plan on its stock ownership
records and send tax information statements to employees and former employees
who transfer title to such shares.

ARTICLE 23 - GOVERNING LAW.

      The validity and construction of the Plan shall be governed by the laws of
The Commonwealth of Massachusetts, without giving effect to the principles of
conflicts of law thereof.

ARTICLE 24 - APPROVAL OF BOARD OF DIRECTORS AND STOCKHOLDERS OF THE COMPANY.

      The Plan was adopted by the Board of Directors on March 15, 2004 and will
be considered for approval by the stockholders of the Company on or before May
5, 2005.