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  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt">As filed with the Securities and Exchange Commission on March&nbsp;23, 2009
  </DIV>
  
  
  <DIV align="right" style="font-size: 10pt; margin-top: 12pt">Registration No.&nbsp;333-
  </DIV>
  
  
  <DIV style="width: 100%; border-bottom: 2pt solid black; font-size: 3pt">&nbsp;</DIV>
  <DIV style="width: 100%; border-bottom: 1pt solid black; font-size: 1pt">&nbsp;</DIV>
  
  
  
  
  <DIV align="center" style="font-size: 14pt; margin-top: 12pt"><B>SECURITIES AND EXCHANGE COMMISSION</B>
  </DIV>
  
  <DIV align="center" style="font-size: 12pt"><B>Washington, D.C. 20549</B>
  </DIV>
  
  <DIV align="center" style="font-size: 18pt; margin-top: 12pt"><B>FORM S-8</B>
  </DIV>
  
  
  <DIV align="center" style="font-size: 12pt; margin-top: 12pt"><B>REGISTRATION STATEMENT UNDER<BR>
  THE SECURITIES ACT OF 1933</B>
  </DIV>
  
  <DIV align="center" style="font-size: 24pt; margin-top: 12pt"><B>NXSTAGE MEDICAL, INC.</B>
  </DIV>
  
  <DIV align="center" style="font-size: 10pt">(Exact Name of Registrant as Specified in Its Charter)</DIV>
  
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
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      <TD width="47%">&nbsp;</TD>
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  <TR valign="bottom">
      <TD align="center" valign="top">Delaware<BR>
  (State or Other Jurisdiction of Incorporation or <BR>
  Organization)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">04-3454702<BR>
  (I.R.S. Employer<BR>
  Identification No.)</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
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      <TD width="47%">&nbsp;</TD>
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      <TD width="47%">&nbsp;</TD>
  </TR>
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  <TR valign="bottom">
      <TD align="center" valign="top">439 South Union Street <BR>
  Lawrence, Massachusetts<BR>
  (Address of Principal Executive Offices)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top"><BR>01843<BR>
  (Zip Code)</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 12pt"><B>2005 Employee Stock Purchase Plan</B><BR>
  (Full Title of the Plan)</DIV>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 12pt"><B>Jeffrey H. Burbank<BR>
  President and Chief Executive Officer<BR>
  439 South Union Street<BR>
  Lawrence, Massachusetts 01843</B><BR>
  (Name and Address of Agent For Service)<BR>
  <B>(978)&nbsp;687-4700</B><BR>
  (Telephone Number, Including Area Code, of Agent For Service)</DIV>
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of &#147;large accelerated filer,&#148; &#147;accelerated filer&#148; and &#147;smaller reporting company&#148; in Rule 12b-2 of the Exchange Act. (Check one):</DIV>
  
  <TABLE width="100%" style="font-size: 10pt; margin-top: 0pt">
  <TR>
  <TD>Large accelerated filer&nbsp;<FONT face="Wingdings">&#111;</FONT></TD>
  <TD align="center">Accelerated filer&nbsp;<FONT face="Wingdings">&#254;</FONT>&nbsp;</TD>
  <TD align="center"><BR>Non-accelerated filer&nbsp;<FONT face="Wingdings">&#111;</FONT><BR>(Do not check if a smaller reporting company)</TD>
  <TD align="right">Smaller reporting company&nbsp;<FONT face="Wingdings">&#111;</FONT></TD>
  </TR>
  </TABLE>
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>CALCULATION OF REGISTRATION FEE</B>
  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
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      <TD width="1%">&nbsp;</TD>
  </TR><TR style="font-size: 1px" valign="bottom">
      <TD nowrap align="left" colspan="23" style="border-bottom: 3px double #000000">&nbsp;</TD>
  </TR>
  <TR style="font-size: 8pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="center">Title of</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Proposed Maximum</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Proposed Maximum</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 8pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="center">Securities to be</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Amount to be</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Offering Price Per</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Aggregate Offering</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Amount of</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 8pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="center">Registered</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Registered(1)</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Share</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Price</TD>
      <TD style="border-right: 2px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="3">Registration Fee</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  
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      <TD width="1%" style="border-top: 2px solid #000000">&nbsp;</TD>
                      <TD style="border-top: 2px solid #000000"><DIV style="margin-left:15px; text-indent:-15px">Common Stock, $.001
  par value per share</DIV></TD>
      <TD style="border-right: 2px solid #000000; border-top: 2px solid #000000">&nbsp;</TD>
      <TD style="border-top: 2px solid #000000">&nbsp;</TD>
      <TD nowrap align="right" style="border-top: 2px solid #000000">&nbsp;</TD>
      <TD align="right" style="border-top: 2px solid #000000">500,000</TD>
      <TD nowrap style="border-top: 2px solid #000000">(2)</TD>
      <TD style="border-right: 2px solid #000000; border-top: 2px solid #000000">&nbsp;</TD>
      <TD style="border-top: 2px solid #000000">&nbsp;</TD>
      <TD nowrap align="right" style="border-top: 2px solid #000000">$</TD>
      <TD align="right" style="border-top: 2px solid #000000">2.30</TD>
      <TD nowrap style="border-top: 2px solid #000000">(3)</TD>
      <TD style="border-right: 2px solid #000000; border-top: 2px solid #000000">&nbsp;</TD>
      <TD style="border-top: 2px solid #000000">&nbsp;</TD>
      <TD nowrap align="right" style="border-top: 2px solid #000000">$</TD>
      <TD align="right" style="border-top: 2px solid #000000">1,150,000</TD>
      <TD nowrap style="border-top: 2px solid #000000">(3)</TD>
      <TD style="border-right: 2px solid #000000; border-top: 2px solid #000000">&nbsp;</TD>
      <TD style="border-top: 2px solid #000000">&nbsp;</TD>
      <TD align="right" style="border-top: 2px solid #000000">$</TD>
      <TD align="right" style="border-top: 2px solid #000000">65.00</TD>
      <TD style="border-top: 2px solid #000000">&nbsp;</TD>
      <TD width="1%" style="border-top: 2px solid #000000">&nbsp;</TD>
  </TR>
  <TR style="font-size: 1px" valign="bottom">
      <TD nowrap align="left" colspan="23" style="border-top: 3px double #000000">&nbsp;</TD>
  </TR>
  
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  <TR>
      <TD width="3%"></TD>
      <TD width="1%"></TD>
      <TD width="96"></TD>
  </TR>
  
  <TR valign="top">
      <TD nowrap align="left">(1)</TD>
      <TD>&nbsp;</TD>
      <TD>In accordance with Rule&nbsp;416 under the Securities Act of 1933, as
  amended, this registration statement shall be deemed to cover any
  additional securities that may from time to time be offered or issued
  to prevent dilution resulting from stock splits, stock dividends or
  similar transactions.</TD>
  </TR>
  
  <TR style="font-size: 3pt"><TD>&nbsp;</TD></TR>
  
  <TR valign="top">
      <TD nowrap align="left">(2)</TD>
      <TD>&nbsp;</TD>
      <TD>Consists of an additional 500,000 shares issuable under the 2005
  Employee Stock Purchase Plan, subject to stockholder approval.</TD>
  </TR>
  
  <TR style="font-size: 3pt"><TD>&nbsp;</TD></TR>
  
  <TR valign="top">
      <TD nowrap align="left">(3)</TD>
      <TD>&nbsp;</TD>
      <TD>Estimated solely for the purpose of calculating the registration fee
  pursuant to Rules 457(c) and 457(h) of the Securities Act of 1933, as
  amended, and based upon the average of the high and low prices of the
  Registrant&#146;s Common Stock as reported on the Nasdaq Global Market on
  March&nbsp;20, 2009.</TD>
  </TR>
  
  </TABLE>
  
  
  
  <DIV style="width: 100%; border-bottom: 1pt solid black; margin-top: 10pt; font-size: 1pt">&nbsp;</DIV>
  <DIV style="width: 100%; border-bottom: 2pt solid black; font-size: 1pt">&nbsp;</DIV>
  
  
  
  
  
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
  </DIV>
  
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  <!-- TOC -->
  <A name="toc"><DIV align="CENTER" style="page-break-before:always"><U><B>TABLE OF CONTENTS</B></U></DIV></A>
  
  <P><CENTER>
  <TABLE border="0" width="90%" cellpadding="0" cellspacing="0">
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  	<TD width="3%"></TD>
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  </TR>
  <TR><TD></TD><TD colspan="8"><A HREF="#000">Item&nbsp;8. Exhibits.</A></TD></TR>
  <TR><TD colspan="9"><A HREF="#001">SIGNATURES</A></TD></TR>
  <TR><TD colspan="9"><A HREF="#002">INDEX TO EXHIBITS</A></TD></TR>
  <TR><TD colspan="9"><A HREF="b74747nmexv5w1.htm">Ex-5.1 Opinion of Wilmer Cutler Pickering Hale and Dorr LLP</A></TD></TR>
  <TR><TD colspan="9"><A HREF="b74747nmexv23w2.htm">Ex-23.2 Consent of Independent Registered Public Accounting Firm</A></TD></TR>
  </TABLE>
  </CENTER>
  <!-- /TOC -->
  <P><HR noshade><P>
  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  
  
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>STATEMENT OF INCORPORATION BY REFERENCE</B>
  </DIV>
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Except as otherwise set forth below, this registration statement on Form S-8 incorporates by
  reference the contents of the registration statement on Form S-8, File No.&nbsp;333-151857, relating to
  the Registrant&#146;s 2005 Employee Stock Purchase Plan, the registration statement on Form S-8, File
  No.&nbsp;333-149225, relating to the Registrant&#146;s 2005 Stock Incentive Plan and 2005 Employee Stock
  Purchase Plan and registration statement on Form S-8, File No.&nbsp;333-130241, relating to the
  Registrant&#146;s 1999 Stock Option and Grant Plan, 2005 Stock Incentive Plan and 2005 Employee Stock
  Purchase Plan.
  </DIV>
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">On December&nbsp;16, 2008, the board of directors of the Registrant approved, subject to stockholder
  approval, an amendment to increase the number of shares available for issuance under the
  Registrant&#146;s 2005 Employee Stock Purchase Plan by 500,000. The Registrant intends to seek
  stockholder approval for such increase, but does not expect to obtain such approval prior to April
  1, 2009, the commencement date for the next Employee Stock Purchase Plan offering period, and
  cannot assure participants that such approval will ever be obtained. While the Registrant may
  grant options relating to the additional 500,000 shares prior to obtaining stockholder approval for
  the increase, such options will not become exercisable unless and until stockholders approve the
  increase. In the event stockholder approval is not obtained, these options will be cancelled and
  become null and void.
  </DIV>
  
  <!-- link2 "Item&nbsp;8. Exhibits." -->
  <DIV align="left"><A NAME="000"></A></DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Item&nbsp;8. Exhibits.</B>
  </DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">The Exhibit&nbsp;Index immediately preceding the exhibits is incorporated by reference.
  </DIV>
  
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->-1-<!-- /Folio -->
  </DIV>
  
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  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  <!-- link1 "SIGNATURES" -->
  <DIV align="left"><A NAME="001"></A></DIV>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>SIGNATURES</B>
  </DIV>
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it
  has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and
  has duly caused this registration statement to be signed on its behalf by the undersigned,
  thereunto duly authorized, in the city of Lawrence, Commonwealth of
  Massachusetts on this 20th day of
  March, 2009.
  </DIV>
  
  <TABLE width="100%" border="0" cellspacing="0" cellpadding="0" style="font-size: 10pt">
  <TR>
      <TD width="48%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="35%">&nbsp;</TD>
      <TD width="15%">&nbsp;</TD>
  </TR>
  <TR>
      <TD valign="top" align="left">&nbsp;</TD>
      <TD colspan="3" align="left">NXSTAGE MEDICAL, INC.<BR>
  &nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR><TR>
      <TD align="left">&nbsp;</TD>
      <TD valign="top">By:&nbsp;&nbsp;</TD>
      <TD colspan="2" style="border-bottom: 1px solid #000000" align="left">/s/ Jeffrey H. Burbank
  &nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR><TR>
      <TD align="left">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD colspan="2" align="left">Jeffrey H. Burbank&nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR><TR>
      <TD align="left">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD colspan="2" align="left">President, Chief Executive Officer&nbsp;</TD>
      <TD>&nbsp;</TD>
  </TR>
  <TR>
      <TD colspan="5">&nbsp;</TD>
  </TR>
  </TABLE>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>POWER OF ATTORNEY AND SIGNATURES</B>
  </DIV>
  
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We, the undersigned officers and directors of NxStage Medical, Inc., hereby severally
  constitute and appoint Jeffrey H. Burbank and Winifred L. Swan, and each of them singly, our true
  and lawful attorneys with full power to them, and each of them singly, to sign for us and in our
  names in the capacities indicated below, the registration statement on Form S-8 filed herewith and
  any and all subsequent amendments to said registration statement, and generally to do all such
  things in our names and on our behalf in our capacities as officers and directors to enable NxStage
  Medical, Inc. to comply with the provisions of the Securities Act of 1933, as amended, and all
  requirements of the Securities and Exchange Commission, hereby ratifying and confirming our
  signatures as they may be signed by our said attorneys, or any of them, to said registration
  statement and any and all amendments thereto.
  </DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pursuant to the requirements of the Securities Act of 1933, this registration statement has
  been signed by the following persons in the capacities and on the dates indicated.
  </DIV>
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
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      <TD width="40%">&nbsp;</TD>
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      <TD width="3%">&nbsp;</TD>
      <TD width="14%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 8pt" valign="bottom">
      <TD nowrap align="CENTER" style="border-bottom: 1px solid #000000"><B>Signature</B></TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" style="border-bottom: 1px solid #000000"><B>Title</B></TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" style="border-bottom: 1px solid #000000"><B>Date</B></TD>
  </TR>
  
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">/s/ Jeffrey H. Burbank
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Jeffrey H. Burbank
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">President, Chief Executive Officer and Director&nbsp;<BR>
  (
  <I>Principal executive officer </I>)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March 20, 2009</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">/s/ Robert S. Brown
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Robert S. Brown
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Chief Financial Officer&nbsp;<BR>
  (
  <I>Principal accounting and financial officer </I>)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March 20, 2009</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">/s/ Philippe O. Chambon
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Philippe O. Chambon
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Director&nbsp;
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March 20, 2009</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">/s/ Daniel A. Giannini
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Daniel A. Giannini
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Director&nbsp;
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March 19, 2009</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Earl R. Lewis
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Director&nbsp;
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March <u>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</u>, 2009</TD>
  </TR>
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      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Reid S. Perper
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Director&nbsp;
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March <u>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</u>, 2009</TD>
  </TR>
  <!-- End Table Body -->
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  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
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  <!-- Begin Table Head -->
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      <TD width="40%">&nbsp;</TD>
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      <TD width="3%">&nbsp;</TD>
      <TD width="14%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 8pt" valign="bottom">
      <TD nowrap align="CENTER" style="border-bottom: 1px solid #000000"><B>Signature</B></TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" style="border-bottom: 1px solid #000000"><B>Title</B></TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" style="border-bottom: 1px solid #000000"><B>Date</B></TD>
  </TR>
  
  <!-- End Table Head -->
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      <TD>&nbsp;</TD>
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      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">/s/ Craig W. Moore
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Craig W. Moore
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Director&nbsp;
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March 19, 2009</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  David S. Utterberg
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Director&nbsp;
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March <u>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</u>, 2009</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">/s/ Jonathan T. Silverstein
  <DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
  Jonathan T. Silverstein
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Director&nbsp;
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March 19, 2009</TD>
  </TR>
  <!-- End Table Body -->
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  </DIV>
  
  
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  <P><HR noshade><P>
  <H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  <!-- link1 "INDEX TO EXHIBITS" -->
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  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
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      <TD width="8%">&nbsp;</TD>
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      <TD width="90%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 8pt" valign="bottom">
      <TD nowrap align="left" style="border-bottom: 1px solid #000000">Number</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="left" style="border-bottom: 1px solid #000000">Description</TD>
  </TR>
  
  <!-- End Table Head -->
  <!-- Begin Table Body -->
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      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.1(1)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Restated Certificate of Incorporation of the Registrant</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">4.2(1)
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Amended and Restated By-Laws of the Registrant</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">5.1
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Opinion of Wilmer Cutler Pickering Hale and Dorr LLP, counsel to the Registrant</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">23.1
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Consent of Wilmer Cutler Pickering Hale and Dorr LLP (included in Exhibit&nbsp;5.1)</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">23.2
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Consent of Independent Registered Public Accounting Firm</TD>
  </TR>
  <TR valign="bottom"><!-- Blank Space -->
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
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  </TR>
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">24.1
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">Power of attorney (included on the signature pages of this registration statement)</TD>
  </TR>
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      <TD nowrap align="left">(1)</TD>
      <TD>&nbsp;</TD>
      <TD>Previously filed with the Securities and Exchange Commission as an
  Exhibit to the Registrant&#146;s Registration Statement on Form S-1, as
  amended (File No.&nbsp;333-126711), and incorporated herein by reference.</TD>
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text: sv8
  Table of Contents
  As filed with the Securities and Exchange Commission on March 23, 2009
  Registration No. 333-
  SECURITIES AND EXCHANGE COMMISSION
  Washington, D.C. 20549
  FORM S-8
  REGISTRATION STATEMENT UNDER
  THE SECURITIES ACT OF 1933
  NXSTAGE MEDICAL, INC.
  (Exact Name of Registrant as Specified in Its Charter)
  Delaware
  (State or Other Jurisdiction of Incorporation or
  Organization)
  04-3454702
  (I.R.S. Employer
  Identification No.)
  439 South Union Street
  Lawrence, Massachusetts
  (Address of Principal Executive Offices)
  01843
  (Zip Code)
  2005 Employee Stock Purchase Plan
  (Full Title of the Plan)
  Jeffrey H. Burbank
  President and Chief Executive Officer
  439 South Union Street
  Lawrence, Massachusetts 01843
  (Name and Address of Agent For Service)
  (978) 687-4700
  (Telephone Number, Including Area Code, of Agent For Service)
  Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act. (Check one):
  Large accelerated filer
  o
  Accelerated filer
  þ
  Non-accelerated filer
  o
  (Do not check if a smaller reporting company)
  Smaller reporting company
  o
  CALCULATION OF REGISTRATION FEE
  Title of
  Proposed Maximum
  Proposed Maximum
  Securities to be
  Amount to be
  Offering Price Per
  Aggregate Offering
  Amount of
  Registered
  Registered(1)
  Share
  Price
  Registration Fee
  Common Stock, $.001
  par value per share
  500,000
  (2)
  $
  2.30
  (3)
  $
  1,150,000
  (3)
  $
  65.00
  (1)
  In accordance with Rule 416 under the Securities Act of 1933, as
  amended, this registration statement shall be deemed to cover any
  additional securities that may from time to time be offered or issued
  to prevent dilution resulting from stock splits, stock dividends or
  similar transactions.
  (2)
  Consists of an additional 500,000 shares issuable under the 2005
  Employee Stock Purchase Plan, subject to stockholder approval.
  (3)
  Estimated solely for the purpose of calculating the registration fee
  pursuant to Rules 457(c) and 457(h) of the Securities Act of 1933, as
  amended, and based upon the average of the high and low prices of the
  Registrant's Common Stock as reported on the Nasdaq Global Market on
  March 20, 2009.
  TABLE OF CONTENTS
  Item 8. Exhibits.
  SIGNATURES
  INDEX TO EXHIBITS
  Ex-5.1 Opinion of Wilmer Cutler Pickering Hale and Dorr LLP
  Ex-23.2 Consent of Independent Registered Public Accounting Firm
  Table of Contents
  STATEMENT OF INCORPORATION BY REFERENCE
  Except as otherwise set forth below, this registration statement on Form S-8 incorporates by
  reference the contents of the registration statement on Form S-8, File No. 333-151857, relating to
  the Registrant's 2005 Employee Stock Purchase Plan, the registration statement on Form S-8, File
  No. 333-149225, relating to the Registrant's 2005 Stock Incentive Plan and 2005 Employee Stock
  Purchase Plan and registration statement on Form S-8, File No. 333-130241, relating to the
  Registrant's 1999 Stock Option and Grant Plan, 2005 Stock Incentive Plan and 2005 Employee Stock
  Purchase Plan.
  On December 16, 2008, the board of directors of the Registrant approved, subject to stockholder
  approval, an amendment to increase the number of shares available for issuance under the
  Registrant's 2005 Employee Stock Purchase Plan by 500,000. The Registrant intends to seek
  stockholder approval for such increase, but does not expect to obtain such approval prior to April
  1, 2009, the commencement date for the next Employee Stock Purchase Plan offering period, and
  cannot assure participants that such approval will ever be obtained. While the Registrant may
  grant options relating to the additional 500,000 shares prior to obtaining stockholder approval for
  the increase, such options will not become exercisable unless and until stockholders approve the
  increase. In the event stockholder approval is not obtained, these options will be cancelled and
  become null and void.
  Item 8. Exhibits.
  The Exhibit Index immediately preceding the exhibits is incorporated by reference.
  -1-
  Table of Contents
  SIGNATURES
  Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it
  has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and
  has duly caused this registration statement to be signed on its behalf by the undersigned,
  thereunto duly authorized, in the city of Lawrence, Commonwealth of
  Massachusetts on this 20th day of
  March, 2009.
  NXSTAGE MEDICAL, INC.
  By:
  /s/ Jeffrey H. Burbank
  Jeffrey H. Burbank
  President, Chief Executive Officer
  POWER OF ATTORNEY AND SIGNATURES
  We, the undersigned officers and directors of NxStage Medical, Inc., hereby severally
  constitute and appoint Jeffrey H. Burbank and Winifred L. Swan, and each of them singly, our true
  and lawful attorneys with full power to them, and each of them singly, to sign for us and in our
  names in the capacities indicated below, the registration statement on Form S-8 filed herewith and
  any and all subsequent amendments to said registration statement, and generally to do all such
  things in our names and on our behalf in our capacities as officers and directors to enable NxStage
  Medical, Inc. to comply with the provisions of the Securities Act of 1933, as amended, and all
  requirements of the Securities and Exchange Commission, hereby ratifying and confirming our
  signatures as they may be signed by our said attorneys, or any of them, to said registration
  statement and any and all amendments thereto.
  Pursuant to the requirements of the Securities Act of 1933, this registration statement has
  been signed by the following persons in the capacities and on the dates indicated.
  Signature
  Title
  Date
  /s/ Jeffrey H. Burbank
  Jeffrey H. Burbank
  President, Chief Executive Officer and Director
  (
  Principal executive officer
  )
  March 20, 2009
  /s/ Robert S. Brown
  Robert S. Brown
  Chief Financial Officer
  (
  Principal accounting and financial officer
  )
  March 20, 2009
  /s/ Philippe O. Chambon
  Philippe O. Chambon
  Director
  March 20, 2009
  /s/ Daniel A. Giannini
  Daniel A. Giannini
  Director
  March 19, 2009
  Earl R. Lewis
  Director
  March
  , 2009
  Reid S. Perper
  Director
  March
  , 2009
  -2-
  Table of Contents
  Signature
  Title
  Date
  /s/ Craig W. Moore
  Craig W. Moore
  Director
  March 19, 2009
  David S. Utterberg
  Director
  March
  , 2009
  /s/ Jonathan T. Silverstein
  Jonathan T. Silverstein
  Director
  March 19, 2009
  -3-
  Table of Contents
  INDEX TO EXHIBITS
  Number
  Description
  4.1(1)
  Restated Certificate of Incorporation of the Registrant
  4.2(1)
  Amended and Restated By-Laws of the Registrant
  5.1
  Opinion of Wilmer Cutler Pickering Hale and Dorr LLP, counsel to the Registrant
  23.1
  Consent of Wilmer Cutler Pickering Hale and Dorr LLP (included in Exhibit 5.1)
  23.2
  Consent of Independent Registered Public Accounting Firm
  24.1
  Power of attorney (included on the signature pages of this registration statement)
  (1)
  Previously filed with the Securities and Exchange Commission as an
  Exhibit to the Registrant's Registration Statement on Form S-1, as
  amended (File No. 333-126711), and incorporated herein by reference.