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                                                                    Exhibit 10.5

                              NxStage Medical, Inc.

                           Restricted Stock Agreement
                     Granted Under 2005 Stock Incentive Plan

         AGREEMENT made this ____ day of _____________, 200[ ], between NxStage
Medical, Inc., a Delaware corporation (the "Company"), and ____________________
(the "Participant").

         For valuable consideration, receipt of which is acknowledged, the
parties hereto agree as follows:

         1.       Purchase of Shares.

         The Company shall issue and sell to the Participant, and the
Participant shall purchase from the Company, subject to the terms and conditions
set forth in this Agreement and in the Company's 2005 Stock Incentive Plan (the
"Plan"), ______ shares (the "Shares") of common stock, $0.001 par value, of the
Company ("Common Stock"), at a purchase price of $[ ] per share. The aggregate
purchase price for the Shares shall be paid by the Participant by check payable
to the order of the Company or such other method as may be acceptable to the
Company. Upon receipt by the Company of payment for the Shares, the Company
shall issue to the Participant one or more certificates in the name of the
Participant for that number of Shares purchased by the Participant. The
Participant agrees that the Shares shall be subject to the purchase options set
forth in Section 2 of this Agreement and the restrictions on transfer set forth
in Section 4 of this Agreement.

         2.       Purchase Option.

                  (a) In the event that the Participant ceases to be employed by
the Company for any reason or no reason, with or without cause, prior to
_______, [ ]_, the Company shall have the right and option (the "Purchase
Option") to purchase from the Participant, for a sum of $[ ] per share (the
"Option Price"), some or all of the Unvested Shares (as defined below).

         "Unvested Shares" means the total number of Shares multiplied by the
Applicable Percentage at the time the Purchase Option becomes exercisable by the
Company. The "Applicable Percentage" shall be (i) 100% during the 12-month
period ending ____________, 200_, (ii) [75%] less [6.25%] for each three months
of employment completed by the Participant with the Company from and after
_________, 200_, and (iii) zero on or after ________, 200__.

                  (b) If the Participant is employed by a parent or subsidiary
of the Company, any references in this Agreement to employment with the Company
or termination of employment by or with the Company shall instead be deemed to
refer to such parent or subsidiary.

         3.       Exercise of Purchase Option and Closing.


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                  (a) The Company may exercise the Purchase Option by delivering
or mailing to the Participant (or his estate), within 90 days after the
termination of the employment of the Participant with the Company, a written
notice of exercise of the Purchase Option. Such notice shall specify the number
of Shares to be purchased. If and to the extent the Purchase Option is not so
exercised by the giving of such a notice within such 90-day period, the Purchase
Option shall automatically expire and terminate effective upon the expiration of
such 90-day period.

                  (b) Within 10 days after delivery to the Participant of the
Company's notice of the exercise of the Purchase Option pursuant to subsection
(a) above, the Participant (or his estate) shall, pursuant to the provisions of
the Joint Escrow Instructions referred to in Section 7 below, tender to the
Company at its principal offices the certificate or certificates representing
the Shares which the Company has elected to purchase in accordance with the
terms of this Agreement, duly endorsed in blank or with duly endorsed stock
powers attached thereto, all in form suitable for the transfer of such Shares to
the Company. Promptly following its receipt of such certificate or certificates,
the Company shall pay to the Participant the aggregate Option Price for such
Shares (provided that any delay in making such payment shall not invalidate the
Company's exercise of the Purchase Option with respect to such Shares).

                  (c) After the time at which any Shares are required to be
delivered to the Company for transfer to the Company pursuant to subsection (b)
above, the Company shall not pay any dividend to the Participant on account of
such Shares or permit the Participant to exercise any of the privileges or
rights of a stockholder with respect to such Shares, but shall, in so far as
permitted by law, treat the Company as the owner of such Shares.

                  (d) The Option Price may be payable, at the option of the
Company, in cancellation of all or a portion of any outstanding indebtedness of
the Participant to the Company or in cash (by check) or both.

                  (e) The Company shall not purchase any fraction of a Share
upon exercise of the Purchase Option, and any fraction of a Share resulting from
a computation made pursuant to Section 2 of this Agreement shall be rounded to
the nearest whole Share (with any one-half Share being rounded upward).

                  (f) The Company may assign its Purchase Option to one or more
persons or entities.

         4.       Restrictions on Transfer.

         The Participant shall not sell, assign, transfer, pledge, hypothecate
or otherwise dispose of, by operation of law or otherwise (collectively
"transfer") any Shares, or any interest therein, that are subject to the
Purchase Option, except that the Participant may transfer such Shares (i) to or
for the benefit of any spouse, children, parents, uncles, aunts, siblings,
grandchildren and any other relatives approved by the Board of Directors
(collectively, "Approved Relatives") or to a trust established solely for the
benefit of the Participant and/or Approved Relatives, provided that such Shares
shall remain subject to this Agreement (including without limitation the
restrictions on transfer set forth in this Section 4 and the Purchase Option)
and such permitted transferee shall, as a condition to such transfer, deliver to
the Company a written instrument confirming



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that such transferee shall be bound by all of the terms and conditions of this
Agreement or (ii) as part of the sale of all or substantially all of the shares
of capital stock of the Company (including pursuant to a merger or
consolidation), provided that, in accordance with the Plan, the securities or
other property received by the Participant in connection with such transaction
shall remain subject to this Agreement.

         5.       Escrow.

         The Participant shall, upon the execution of this Agreement, execute
Joint Escrow Instructions in the form attached to this Agreement as Exhibit A.
The Joint Escrow Instructions shall be delivered to the Secretary of the
Company, as escrow agent thereunder. The Participant shall deliver to such
escrow agent a stock assignment duly endorsed in blank, in the form attached to
this Agreement as Exhibit B, and hereby instructs the Company to deliver to such
escrow agent, on behalf of the Participant, the certificate(s) evidencing the
Shares issued hereunder. Such materials shall be held by such escrow agent
pursuant to the terms of such Joint Escrow Instructions.

         6.       Restrictive Legends.

         All certificates representing Shares shall have affixed thereto legends
in substantially the following form, in addition to any other legends that may
be required under federal or state securities laws:

                  "The shares of stock represented by this certificate are
                  subject to restrictions on transfer and an option to purchase
                  set forth in a certain Restricted Stock Agreement between the
                  corporation and the registered owner of these shares (or his
                  predecessor in interest), and such Agreement is available for
                  inspection without charge at the office of the Secretary of
                  the corporation."

         7.       Provisions of the Plan.

                  (a) This Agreement is subject to the provisions of the Plan, a
copy of which is furnished to the Participant with this Agreement.

                  (b) As provided in the Plan, upon the occurrence of a
Reorganization Event (as defined in the Plan), the repurchase and other rights
of the Company hereunder shall inure to the benefit of the Company's successor
and shall apply to the cash, securities or other property which the Shares were
converted into or exchanged for pursuant to such Reorganization Event in the
same manner and to the same extent as they applied to the Shares under this
Agreement. If, in connection with a Reorganization Event, a portion of the cash,
securities and/or other property received upon the conversion or exchange of the
Shares is to be placed into escrow to secure indemnification or similar
obligations, the mix between the vested and unvested portion of such cash,
securities and/or other property that is placed into escrow shall be the same as
the mix between the vested and unvested portion of such cash, securities and/or
other property that is not subject to escrow.



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         8.       Withholding Taxes; Section 83(b) Election.

                  (a) The Participant acknowledges and agrees that the Company
has the right to deduct from payments of any kind otherwise due to the
Participant any federal, state or local taxes of any kind required by law to be
withheld with respect to the purchase of the Shares by the Participant or the
lapse of the Purchase Option.

                  (b) The Participant has reviewed with the Participant's own
tax advisors the federal, state, local and foreign tax consequences of this
investment and the transactions contemplated by this Agreement. The Participant
is relying solely on such advisors and not on any statements or representations
of the Company or any of its agents. The Participant understands that the
Participant (and not the Company) shall be responsible for the Participant's own
tax liability that may arise as a result of this investment or the transactions
contemplated by this Agreement. The Participant understands that it may be
beneficial in many circumstances to elect to be taxed at the time the Shares are
purchased rather than when and as the Company's Purchase Option expires by
filing an election under Section 83(b) of the Internal Revenue Code of 1986 with
the I.R.S. within 30 days from the date of purchase.

                  THE PARTICIPANT ACKNOWLEDGES THAT IT IS SOLELY THE
PARTICIPANT'S RESPONSIBILITY AND NOT THE COMPANY'S TO FILE TIMELY THE ELECTION
UNDER SECTION 83(b), EVEN IF THE PARTICIPANT REQUESTS THE COMPANY OR ITS
REPRESENTATIVES TO MAKE THIS FILING ON THE PARTICIPANT'S BEHALF.

         9.       Miscellaneous.

                  (a) No Rights to Employment. The Participant acknowledges and
agrees that the vesting of the Shares pursuant to Section 2 hereof is earned
only by continuing service as an employee at the will of the Company (not
through the act of being hired or purchasing shares hereunder). The Participant
further acknowledges and agrees that the transactions contemplated hereunder and
the vesting schedule set forth herein do not constitute an express or implied
promise of continued engagement as an employee or consultant for the vesting
period, for any period, or at all.

                  (b) Severability. The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability of
any other provision of this Agreement, and each other provision of this
Agreement shall be severable and enforceable to the extent permitted by law.

                  (c) Waiver. Any provision for the benefit of the Company
contained in this Agreement may be waived, either generally or in any particular
instance, by the Board of Directors of the Company.

                  (d) Binding Effect. This Agreement shall be binding upon and
inure to the benefit of the Company and the Participant and their respective
heirs, executors, administrators, legal representatives, successors and assigns,
subject to the restrictions on transfer set forth in Sections 4 and 5 of this
Agreement.



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                  (e) Notice. All notices required or permitted hereunder shall
be in writing and deemed effectively given upon personal delivery or five days
after deposit in the United States Post Office, by registered or certified mail,
postage prepaid, addressed to the other party hereto at the address shown
beneath his or its respective signature to this Agreement, or at such other
address or addresses as either party shall designate to the other in accordance
with this Section 12(e).

                  (f) Pronouns. Whenever the context may require, any pronouns
used in this Agreement shall include the corresponding masculine, feminine or
neuter forms, and the singular form of nouns and pronouns shall include the
plural, and vice versa.

                  (g) Entire Agreement. This Agreement and the Plan constitute
the entire agreement between the parties, and supersedes all prior agreements
and understandings, relating to the subject matter of this Agreement.

                  (h) Amendment. This Agreement may be amended or modified only
by a written instrument executed by both the Company and the Participant.

                  (i) Governing Law. This Agreement shall be construed,
interpreted and enforced in accordance with the internal laws of the State of
Delaware without regard to any applicable conflicts of laws.

                  (j) Participant's Acknowledgments. The Participant
acknowledges that he or she: (i) has read this Agreement; (ii) has been
represented in the preparation, negotiation, and execution of this Agreement by
legal counsel of the Participant's own choice or has voluntarily declined to
seek such counsel; (iii) understands the terms and consequences of this
Agreement; (iv) is fully aware of the legal and binding effect of this
Agreement; and (v) understands that the law firm of Wilmer Cutler Pickering Hale
and Dorr LLP, is acting as counsel to the Company in connection with the
transactions contemplated by the Agreement, and is not acting as counsel for the
Participant.




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         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

                                          NXSTAGE MEDICAL, INC.

                                          By:
                                             -----------------------------------
                                             Title:
                                                   -----------------------------
                                          Address:
                                                   -----------------------------

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



                                          --------------------------------------
                                          [Name of Participant]

                                          Address:
                                                   -----------------------------

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



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                                    Exhibit A

                              NxStage Medical, Inc.

                            Joint Escrow Instructions

                                   __________, [    ]




Secretary
NxStage Medical, Inc.
439 South Union Street
Lawrence, MA 01843

Dear Sir:

         As Escrow Agent for NxStage Medical, Inc., a Delaware corporation, and
its successors in interest under the Restricted Stock Agreement (the
"Agreement") of even date herewith, to which a copy of these Joint Escrow
Instructions is attached (the "Company"), and the undersigned person ("Holder"),
you are hereby authorized and directed to hold the documents delivered to you
pursuant to the terms of the Agreement in accordance with the following
instructions:

         1.       Appointment. Holder irrevocably authorizes the Company to
deposit with you any certificates evidencing Shares (as defined in the
Agreement) to be held by you hereunder and any additions and substitutions to
said Shares. For purposes of these Joint Escrow Instructions, "Shares" shall be
deemed to include any additional or substitute property. Holder does hereby
irrevocably constitute and appoint you as his attorney-in-fact and agent for the
term of this escrow to execute with respect to such Shares all documents
necessary or appropriate to make such Shares negotiable and to complete any
transaction herein contemplated. Subject to the provisions of this Section 1 and
the terms of the Agreement, Holder shall exercise all rights and privileges of a
stockholder of the Company while the Shares are held by you.

         2.       Closing of Purchase.

                  (a)      Upon any purchase by the Company of the Shares
pursuant to the Agreement, the Company shall give to Holder and you a written
notice specifying the purchase price for the Shares, as determined pursuant to
the Agreement, and the time for a closing hereunder (the "Closing") at the
principal office of the Company. Holder and the Company hereby irrevocably
authorize and direct you to close the transaction contemplated by such notice in
accordance with the terms of said notice.

                  (b)      At the Closing, you are directed (i) to date the
stock assignment form or forms necessary for the transfer of the Shares, (ii) to
fill in on such form or forms the number of Shares being transferred, and (iii)
to deliver same, together with the certificate or certificates



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evidencing the Shares to be transferred, to the Company against the simultaneous
delivery to you of the purchase price for the Shares being purchased pursuant to
the Agreement.

         3.       Withdrawal. The Holder shall have the right to withdraw from
this escrow any Shares as to which the Purchase Option (as defined in the
Agreement) has terminated or expired.

         4.       Duties of Escrow Agent.

                  (a)      Your duties hereunder may be altered, amended,
modified or revoked only by a writing signed by all of the parties hereto.

                  (b)      You shall be obligated only for the performance of
such duties as are specifically set forth herein and may rely and shall be
protected in relying or refraining from acting on any instrument reasonably
believed by you to be genuine and to have been signed or presented by the proper
party or parties. You shall not be personally liable for any act you may do or
omit to do hereunder as Escrow Agent or as attorney-in-fact of Holder while
acting in good faith and in the exercise of your own good judgment, and any act
done or omitted by you pursuant to the advice of your own attorneys shall be
conclusive evidence of such good faith.

                  (c)      You are hereby expressly authorized to disregard any
and all warnings given by any of the parties hereto or by any other person or
entity, excepting only orders or process of courts of law, and are hereby
expressly authorized to comply with and obey orders, judgments or decrees of any
court. If you are uncertain of any actions to be taken or instructions to be
followed, you may refuse to act in the absence of an order, judgment or decrees
of a court. In case you obey or comply with any such order, judgment or decree
of any court, you shall not be liable to any of the parties hereto or to any
other person or entity, by reason of such compliance, notwithstanding any such
order, judgment or decree being subsequently reversed, modified, annulled, set
aside, vacated or found to have been entered without jurisdiction.

                  (d)      You shall not be liable in any respect on account of
the identity, authority or rights of the parties executing or delivering or
purporting to execute or deliver the Agreement or any documents or papers
deposited or called for hereunder.

                  (e)      You shall be entitled to employ such legal counsel
and other experts as you may deem necessary properly to advise you in connection
with your obligations hereunder and may rely upon the advice of such counsel.

                  (f)      Your rights and responsibilities as Escrow Agent
hereunder shall terminate if (i) you cease to be Secretary of the Company or
(ii) you resign by written notice to each party. In the event of a termination
under clause (i), your successor as Secretary shall become Escrow Agent
hereunder; in the event of a termination under clause (ii), the Company shall
appoint a successor Escrow Agent hereunder.

                  (g)      If you reasonably require other or further
instruments in connection with these Joint Escrow Instructions or obligations in
respect hereto, the necessary parties hereto shall join in furnishing such
instruments.



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                  (h)      It is understood and agreed that if you believe a
dispute has arisen with respect to the delivery and/or ownership or right of
possession of the securities held by you hereunder, you are authorized and
directed to retain in your possession without liability to anyone all or any
part of said securities until such dispute shall have been settled either by
mutual written agreement of the parties concerned or by a final order, decree or
judgment of a court of competent jurisdiction after the time for appeal has
expired and no appeal has been perfected, but you shall be under no duty
whatsoever to institute or defend any such proceedings.

                  (i)      These Joint Escrow Instructions set forth your sole
duties with respect to any and all matters pertinent hereto and no implied
duties or obligations shall be read into these Joint Escrow Instructions against
you.

                  (j)      The Company shall indemnify you and hold you harmless
against any and all damages, losses, liabilities, costs, and expenses, including
attorneys' fees and disbursements, (including without limitation the fees of
counsel retained pursuant to Section 4(e) above, for anything done or omitted to
be done by you as Escrow Agent in connection with this Agreement or the
performance of your duties hereunder, except such as shall result from your
gross negligence or willful misconduct.

5.       Notice. Any notice required or permitted hereunder shall be given in
writing and shall be deemed effectively given upon personal delivery or upon
deposit in the United States Post Office, by registered or certified mail with
postage and fees prepaid, addressed to each of the other parties thereunto
entitled at the following addresses, or at such other addresses as a party may
designate by ten days' advance written notice to each of the other parties
hereto.

         COMPANY:          Notices to the Company shall be sent to the
                           address set forth in the salutation hereto,
                           Attn: President

         HOLDER:           Notices to Holder shall be sent to the address
                           set forth below Holder's signature below.

         ESCROW AGENT:     Notices to the Escrow Agent shall be sent to the
                           address set forth in the salutation hereto.

6.       Miscellaneous.

                  (a)      By signing these Joint Escrow Instructions, you
become a party hereto only for the purpose of said Joint Escrow Instructions,
and you do not become a party to the Agreement.



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                  (b)      This instrument shall be binding upon and inure to
the benefit of the parties hereto and their respective successors and permitted
assigns.

                                         Very truly yours,

                                         NxStage Medical, Inc.

                                         By:
                                            ------------------------------------
                                         Title:
                                               ---------------------------------

                                         HOLDER:



                                         ---------------------------------------
                                                      (Signature)


                                         ---------------------------------------
                                                      Print Name

                                         Address:
                                                  ------------------------------

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

                                         Date Signed:
                                                     ---------------------------
ESCROW AGENT:
----------------------------------






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                                    Exhibit B

                                    (STOCK ASSIGNMENT SEPARATE FROM CERTIFICATE)




         FOR VALUE RECEIVED, I hereby sell, assign and transfer unto
__________________ (_________) shares of Common Stock, $0.001 par value per
share, of NxStage Medical, Inc. (the "Corporation") standing in my name on the
books of the Corporation represented by Certificate(s) Number __________
herewith, and do hereby irrevocably constitute and appoint
______________________ attorney to transfer the said stock on the books of the
Corporation with full power of substitution in the premises.

                                         Dated:
                                                --------------------------------


IN PRESENCE OF
                                         ---------------------------------------


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


         NOTICE: The signature(s) to this assignment must correspond with the
name as written upon the face of the certificate, in every particular, without
alteration, enlargement, or any change whatever and must be guaranteed by a
commercial bank, trust company or member firm of the Boston, New York or Midwest
Stock Exchange.


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