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                                                                   EXHIBIT 10.18

                          CONCORD COMMUNICATIONS, INC.

         NON-QUALIFIED STOCK OPTION AGREEMENT FOR NON-EMPLOYEE DIRECTORS

      1. Grant Under 1997 Non-Employee Director Stock Option Plan. This option
is granted pursuant to and is governed by the Company's 1997 Non-Employee
Director Stock Option Plan (the "Plan") and, unless the context otherwise
requires, terms used herein shall have the meanings assigned to them in the
Plan. Determinations made in connection with this option pursuant to the Plan
shall be governed by the Plan as it exists on the date hereof. In the event of
any conflict between this Agreement and the provisions of the Plan, the Plan
shall govern.

      2. Grant as Non-Qualified Option; Other Options. This option is intended
to be a non-qualified option (rather than an incentive stock option) granted
pursuant to Section 4(b) of the Plan, and the Board of Directors of the Company
(the "Board") intends to take appropriate action, if necessary, to achieve this
result. This option is in addition to any other options heretofore or hereafter
granted to the Optionee by the Company, but a duplicate original of this
instrument shall not affect the grant of another option.

      3. Exercise of Option if Service as a Director Continues. Unless sooner
terminated pursuant to Section 4 hereof, this option shall vest in the Optionee
and thus become exercisable in accordance with the vesting schedule set forth in
Section 7 of the Plan, provided that the Optionee has continuously served as a
member of the Board through such vesting date. This option shall expire on the
date, which is ten (10) years from the date this option is granted.

      4. Termination of Option Rights.

            (a)   In the event that Optionee ceases to be a member of the Board
                  for any reason other than death or permanent disability, any
                  then unexercised portion of this option shall, to the extent
                  not then vested, immediately terminate and become void. Any
                  portion of this option which is vested but has not been
                  exercised at the time the Optionee so ceases to be a member of
                  the Board may be exercised, to the extent it is then vested,
                  by the Optionee within 60 days of the date the Optionee ceased
                  to be a member of the Board, and this option shall terminate
                  after such 60 days has expired.

            (b)   In the event that the Optionee ceases to be a member of the
                  Board by reason of his or her permanent disability or death,
                  this option may be exercised, to the extent of the number of
                  shares with respect to which he or she could have exercised it
                  on the date of death or permanent disability, by the Optionee
                  (or by Optionee's personal representative, heir or legatee, in
                  the event of death) until the scheduled expiration date of the
                  option.

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      5. Exercise. To the extent then exercisable, the Optionee may exercise
this option in whole or in part at any time and from time to time as provided by
the terms of this Agreement and the Plan, except that this option may not be
exercised for a fraction of a share unless such exercise is with respect to the
final installment of stock subject to this option and a fractional share (or
cash in lieu thereof) would otherwise be required to be issued to permit the
Optionee to exercise completely such final installment. Any fractional share
with respect to which an installment of this option cannot be exercised because
of the limitation contained in the preceding sentence shall remain subject to
this option and shall be available for later purchase by the Optionee in
accordance with the terms hereof. There shall be no such exercise at any one
time as to fewer than one hundred (100) shares or all of the remaining shares
then purchasable by the person or persons exercising the option, if fewer than
one hundred (100) shares.

      6. Payment of Price. The option price is payable in United States dollars
and may be paid: (a) in cash or by check, or any combination of the foregoing,
equal in amount to the option price; (b) in whole or in part in shares of the
Common Stock of the Company already owned by the person or persons exercising
the option or shares subject to the option being exercised (subject to such
restrictions and guidelines as the Board may adopt from time to time), valued at
fair market value determined in accordance with the provisions of Section 5 of
the Plan; or (c) consistent with applicable law, through the delivery of an
assignment to the Company of a sufficient amount of the proceeds from the sale
of Option Shares acquired upon exercise of this option and an authorization to
the broker or selling agent to pay that amount to the Company, which shall be at
the Optionee's direction at the time of exercise.

      7. Method of Exercising Option. Subject to the terms and conditions of the
Plan and this Agreement, this option may be exercised by written notice to the
Company by mail or in person, addressed to the Chief Financing Officer at 400
Nickerson Road, Marlboro, Massachusetts 01752, its principal executive offices.
Such notice shall state the election to exercise this option and the number of
shares in respect of which it is being exercised and shall be signed by the
person or persons so exercising this option. Such notice shall be accompanied by
payment of the full purchase price of such shares. The Company's transfer agent
shall, on behalf of the Company, prepare a certificate or certificates
representing Option Shares acquired upon exercise of this option, shall register
the Optionee (or the Optionee's personal representative, heir or legatee if this
option is being exercised pursuant to Section 4 hereof) as the owner of the
Option Shares on the books of the Company and shall cause the fully executed
certificate(s) representing such shares to be delivered to the Optionee (or the
Optionee's personal representative, heir or legatee if this option is being
exercised pursuant to Section 4 hereof) as soon as practicable after payment of
the option price in full. In the event this option shall be exercised, pursuant
to Section 4 hereof, by any person or persons other than the Optionee, such
notice shall be accompanied by appropriate proof of the right of such person or
persons to exercise this option. All shares that shall be purchased upon the
exercise of this option as provided herein shall be fully paid and
non-assessable.


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      8. Option Not Transferable. This option is not transferable or assignable
except by will or by the laws of descent and distribution or pursuant to a
domestic relations order. During the Optionee's lifetime only the Optionee can
exercise the option.

      9. No Obligation to Exercise Option. The grant and acceptance of this
option imposes no obligation on the Optionee to exercise it.

      10. No Rights As Stockholder until Exercise. The Optionee shall have no
rights as a stockholder with respect to any of the Option Shares until a stock
certificate therefore has been issued to the Optionee and is fully paid for.
Except as is expressly provided in Section 10 of the Plan with respect to
certain changes in the capitalization of the Company, no adjustment shall be
made for dividends or similar rights for which the record date is prior to the
date such stock certificate is issued.

      11. Capital Changes and Business Successions. The Plan contains extensive
provisions designed to preserve options at full value in a number of
contingencies. Therefore, provisions in the Plan for adjustment with respect to
stock subject to options and the related provisions with respect to successors
to the business of the Company are hereby made applicable hereunder and are
incorporated herein by reference.

      12. Withholding Taxes. The Optionee hereby acknowledges that the Company
may be required to withhold federal, state and local taxes attributable to the
Optionee's exercise of any installment of this option and therefore agrees to
pay the Company any such amounts upon the Company's request.

      13. Agreement to Purchase for Investment. By acceptance of this option,
the Optionee agrees that a purchase of shares under this option will be made for
investment and will not be made with a view to their distribution, as that term
is used in the Securities Act of 1933, unless in the opinion of counsel to the
Company such transaction is in compliance with or exempt from the registration
and prospectus requirements of that Act. The Optionee agrees to sign a
certification to such effect at the time of exercising this option and agrees
that the certificate for the shares so purchased may be enscribed with a legend
to ensure compliance with the Securities Act of 1933 and with any other
applicable securities laws. The certificates representing such shares shall
carry such appropriate legend and such written instructions with respect thereto
shall be given to the Company's transfer agent, as may be deemed necessary or
advisable by counsel to the Company in order to comply with the requirements of
the Securities Act of 1933 or any state securities laws.

      14. Resale Restrictions. Under no circumstances may shares acquired
hereunder be disposed of on or prior to the date that is six months after the
date that this option was granted.


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      15. Governing Law. This Agreement constitutes the entire agreement of the
parties with respect to the subject matter hereof, supersedes any and all
correspondence, discussions or agreements between the parties regarding equity
incentives for the Optionee and satisfies all of the Company's obligations with
respect to the grant of equity incentives to the Optionee as in effect on the
date hereof.

      IN WITNESS WHEREOF the Company and the Optionee have caused this
instrument to be executed, and the Optionee whose signature appears below
acknowledges receipt of a copy of the Plan and acceptance of an original copy of
this Agreement.

                                                    CONCORD COMMUNICATIONS, INC.
                                                    400 Nickerson Road
                                                    Marlboro, MA  01752

                                                    By: ________________________
                                                        Name:
                                                        Title:

                                                    ____________________________
                                                    (OPTIONEE)

                                                    ____________________________
                                                    Street Address

                                                    ____________________________
                                                    City        State   Zip Code