content: <HTML>
  <HEAD>
  <TITLE>sv8</TITLE>
  </HEAD>
  <BODY bgcolor="#FFFFFF">
  <!-- PAGEBREAK -->
  <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 April&nbsp;2, 2007
  </DIV>
  
  
  <DIV align="right" style="font-size: 10pt; margin-top: 2pt">Registration No.&nbsp;333-&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  </DIV>
  
  
  <DIV style="width: 100%; border-bottom: 2pt solid black; font-size: 1pt">&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 -->
  <TR valign="bottom">
      <TD width="47%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="47%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom">
      <TD align="center" valign="top">Delaware<BR>
  (State or Other Jurisdiction of Incorporation <BR>
  or 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%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="47%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="47%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <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: 18pt"><B>2005 Stock Incentive Plan</B><BR>
  (Full Title of the Plan)
  </DIV>
  
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><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="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%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="1%">&nbsp;</TD>
      <TD width="50%">&nbsp;</TD>
      <TD width="2%">&nbsp;</TD><!-- VRule -->
      <TD width="3%">&nbsp;</TD>
      <TD width="3%">&nbsp;</TD>
      <TD width="3%">&nbsp;</TD>
      <TD width="3%">&nbsp;</TD>
      <TD width="2%">&nbsp;</TD><!-- VRule -->
      <TD width="2%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="2%">&nbsp;</TD><!-- VRule -->
      <TD width="2%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="2%">&nbsp;</TD><!-- VRule -->
      <TD width="2%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
  
      <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: 10pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2">Proposed Maximum</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2">Proposed Maximum</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="left">&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2">Amount to be</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2">Offering Price Per</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2">Aggregate Offering</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2">Amount of</TD>
      <TD>&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" valign="bottom">    <TD width="1%">&nbsp;</TD>
  
      <TD nowrap align="center" style="border-bottom: 0px solid #000000">Title of Securities to be Registered</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2" style="border-bottom: 0px solid #000000">&nbsp;&nbsp;&nbsp;&nbsp;Registered(1)&nbsp;&nbsp;&nbsp;&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2" style="border-bottom: 0px solid #000000">Share</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2" style="border-bottom: 0px solid #000000">Price</TD>
      <TD>&nbsp;</TD>
      <TD style="border-right: 1px solid #000000">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD nowrap align="center" colspan="2" style="border-bottom: 0px solid #000000">Registration Fee</TD>
      <TD>&nbsp;</TD>
      <TD width="1%">&nbsp;</TD>
  </TR>
  
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom">
      <TD width="1%" style="border-top: 1px solid #000000">&nbsp;</TD>
                      <TD style="border-top: 1px solid #000000"><DIV style="margin-left:15px; text-indent:-15px">Common Stock,
  $0.001 par value
  per share</DIV></TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
  
      <TD colspan="4" align="center" style="border-top: 1px solid #000000">600,000&nbsp;shares(2)</TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD nowrap align="left" style="border-top: 1px solid #000000">&nbsp;</TD>
  
  <TD colspan="1" align="center" style="border-top: 1px solid #000000">$13.40(3)</TD>
      <TD nowrap style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD nowrap align="left" style="border-top: 1px solid #000000">&nbsp;</TD>
  
  <TD align="center" style="border-top: 1px solid #000000">$8,040,000(3)</TD>
      <TD nowrap style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-right: 1px solid #000000; border-top: 1px solid #000000">&nbsp;</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD align="left" style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD align="center" style="border-top: 1px solid #000000">$246.83</TD>
      <TD style="border-top: 1px solid #000000">&nbsp;</TD>
      <TD width="1%" style="border-top: 1px 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>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(1)</TD>
      <TD width="1%">&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>
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(2)</TD>
      <TD width="1%">&nbsp;</TD>
      <TD>Consists of an additional 600,000 shares issuable under the 2005 Stock Incentive Plan.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <DIV style="margin-top: 6pt">
  <TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">
  
  <TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
      <TD width="1%" nowrap align="left">(3)</TD>
      <TD width="1%">&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;30, 2007.</TD>
  </TR>
  
  </TABLE>
  </DIV>
  
  <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>
  
  <!-- PAGEBREAK -->
  <P><HR noshade><P>
  
  <DIV style="font-family: 'Times New Roman',Times,serif">
  
  
  
  
  
  
  <!-- 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">
  <TR>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="3%"></TD>
  	<TD width="76%"></TD>
  </TR>
  <TR><TD colspan="9"><A HREF="#000">STATEMENT OF INCORPORATION BY REFERENCE</A></TD></TR>
  <TR><TD></TD><TD colspan="8"><A HREF="#001">Item&nbsp;8. Exhibits.</A></TD></TR>
  <TR><TD colspan="9"><A HREF="#002">SIGNATURES</A></TD></TR>
  <TR><TD colspan="9"><A HREF="#003">INDEX TO EXHIBITS</A></TD></TR>
  <TR><TD colspan="9"><A HREF="b64520nmexv5w1.htm">Ex-5.1 Opinion of Wilmer Cutler Pickering Hale and Dorr LLP</A></TD></TR>
  <TR><TD colspan="9"><A HREF="b64520nmexv23w2.htm">Ex-23.2 Consent of Ernst & Young LLP</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>
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  <!-- link1 "STATEMENT OF INCORPORATION BY REFERENCE" -->
  <DIV align="left"><A NAME="000"></A></DIV>
  
  <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;&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;333-130291, relating to
  the Registrant&#146;s 1999 Stock Option and Grant Plan, 2005 Stock Incentive Plan and 2005 Employee
  Stock Purchase Plan.
  </DIV>
  <!-- link2 "Item&nbsp;8. Exhibits." -->
  <DIV align="left"><A NAME="001"></A></DIV>
  
  <DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Item&nbsp;8.&nbsp;&nbsp; Exhibits.</B>
  </DIV>
  
  
  <DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Exhibit&nbsp;Index immediately preceding the exhibits is incorporated by reference.
  </DIV>
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->-1-<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <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 "SIGNATURES" -->
  <DIV align="left"><A NAME="002"></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;&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 Lawrence, Massachusetts on this 29<SUP style="font-size: 85%; vertical-align: text-top">th</SUP>
  day of March, 2007.
  </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</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;&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;&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 -->
  <TR valign="bottom">
      <TD width="30%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="30%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="15%">&nbsp;</TD>
  </TR>
  <TR style="font-size: 10pt" 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 align="right">&nbsp;</TD>
      <TD>&nbsp;</TD>
      <TD align="center" nowrap valign="top"><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top">&nbsp;</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Jeffrey H. Burbank<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Jeffrey H. Burbank</TD>
      <TD>&nbsp;</TD>
      <TD align="left">
  President, Chief Executive
  Officer and Director<br>
  (<I>Principal executive officer</I>)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;29, 2007</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Robert S. Brown<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Robert S. Brown</TD>
      <TD>&nbsp;</TD>
      <TD align="left">
  Chief Financial Officer
  <br>(<I>Principal accounting and
  financial officer</I>)
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;29, 2007</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Philippe O. Chambon<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Philippe O. Chambon, M.D., Ph.D.</TD>
      <TD>&nbsp;</TD>
      <TD valign="top" align="left">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;30, 2007</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Daniel A. Giannini<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Daniel A. Giannini</TD>
      <TD>&nbsp;</TD>
      <TD valign="top" align="left">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;29, 2007</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Reid S. Perper<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Reid S. Perper</TD>
      <TD>&nbsp;</TD>
      <TD valign="top" align="left">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;29, 2007</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Peter P. Phildius<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Peter P. Phildius</TD>
      <TD>&nbsp;</TD>
      <TD valign="top" align="left">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;28, 2007</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->-2-<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <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">
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="30%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="30%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="15%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ Craig W. Moore<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  Craig W. Moore</TD>
      <TD>&nbsp;</TD>
      <TD valign="top" align="left">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;29, 2007</TD>
  </TR>
  <TR valign="bottom" style="padding-top: 1em">
      <TD align="left" nowrap valign="top">/s/ David S. Utterberg<BR>
  <DIV style="font-size: 1pt; border-bottom: 1px solid #000000">&nbsp;</DIV>
  David S. Utterberg</TD>
      <TD>&nbsp;</TD>
      <TD valign="top" align="left">
  Director
  </TD>
      <TD>&nbsp;</TD>
      <TD align="center" valign="top">March&nbsp;30, 2007</TD>
  </TR>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->-3-<!-- /Folio -->
  </DIV>
  
  <!-- PAGEBREAK -->
  <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" -->
  <DIV align="left"><A NAME="003"></A></DIV>
  
  <DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>INDEX TO EXHIBITS</B>
  </DIV>
  
  <DIV align="center">
  <TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
  <!-- Begin Table Head -->
  <TR valign="bottom">
      <TD width="10%">&nbsp;</TD>
      <TD width="5%">&nbsp;</TD>
      <TD width="85%">&nbsp;</TD>
  </TR>
  <!-- End Table Head -->
  <!-- Begin Table Body -->
  <TR valign="bottom">
      <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px"><u>Number</u>
  </DIV></TD>
      <TD>&nbsp;</TD>
      <TD align="left" valign="top"><u>Description</u></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">4.1(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)</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 Ernst &#038; Young LLP</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">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>
  <!-- End Table Body -->
  </TABLE>
  </DIV>
  
  
  
  <DIV align="left">
  <DIV style="font-size: 3pt; margin-top: 16pt; width: 18%; border-top: 1px solid #000000">&nbsp;</DIV>
  </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>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>
  </TR>
  
  </TABLE>
  
  
  <P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
  </DIV>
  
  </BODY>
  </HTML>
metadata_documents: [{"type": "S-8", "sequence": "1", "filename": "b64520nmsv8.htm", "description": "NXSTAGE MEDICAL, INC.", "secsgml_size_bytes": 25456}]
metadata_filer: {"company-data": {"conformed-name": "NxStage Medical, Inc.", "cik": "0001333170", "assigned-sic": "3845", "irs-number": "043454702", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-141804", "film-number": "07740010"}, "business-address": {"street1": "439 SOUTH UNION STREET", "street2": "5TH FLOOR", "city": "LAWRENCE", "state": "MA", "zip": "01843", "phone": "978-687-4700"}, "mail-address": {"street1": "439 SOUTH UNION STREET", "street2": "5TH FLOOR", "city": "LAWRENCE", "state": "MA", "zip": "01843"}}
text: sv8
  Table of Contents
  As filed with the Securities and Exchange Commission
  on April 2, 2007
  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 Stock Incentive 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)
  CALCULATION OF REGISTRATION FEE
  Proposed Maximum
  Proposed Maximum
  Amount to be
  Offering Price Per
  Aggregate Offering
  Amount of
  Title of Securities to be Registered
  Registered(1)
  Share
  Price
  Registration Fee
  Common Stock,
  $0.001 par value
  per share
  600,000 shares(2)
  $13.40(3)
  $8,040,000(3)
  $246.83
  (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 600,000 shares issuable under the 2005 Stock Incentive Plan.
  (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 30, 2007.
  TABLE OF CONTENTS
  STATEMENT OF INCORPORATION BY REFERENCE
  Item 8. Exhibits.
  SIGNATURES
  INDEX TO EXHIBITS
  Ex-5.1 Opinion of Wilmer Cutler Pickering Hale and Dorr LLP
  Ex-23.2 Consent of Ernst & Young LLP
  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. 333-130291, relating to
  the Registrant's 1999 Stock Option and Grant Plan, 2005 Stock Incentive Plan and 2005 Employee
  Stock Purchase Plan.
  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 Lawrence, Massachusetts on this 29
  th
  day of March, 2007.
  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 29, 2007
  /s/ Robert S. Brown
  Robert S. Brown
  Chief Financial Officer
  (
  Principal accounting and
  financial officer
  )
  March 29, 2007
  /s/ Philippe O. Chambon
  Philippe O. Chambon, M.D., Ph.D.
  Director
  March 30, 2007
  /s/ Daniel A. Giannini
  Daniel A. Giannini
  Director
  March 29, 2007
  /s/ Reid S. Perper
  Reid S. Perper
  Director
  March 29, 2007
  /s/ Peter P. Phildius
  Peter P. Phildius
  Director
  March 28, 2007
  -2-
  Table of Contents
  /s/ Craig W. Moore
  Craig W. Moore
  Director
  March 29, 2007
  /s/ David S. Utterberg
  David S. Utterberg
  Director
  March 30, 2007
  -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)
  23.2
  Consent of Ernst & Young LLP
  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.