NxStage Appoints Jonathan Silverstein to Board of Directors

Thursday July 24, 2008

LAWRENCE, Mass., July 24 /PRNewswire-FirstCall/ — NxStage Medical, Inc. (Nasdaq: NXTM), a leading manufacturer of innovative dialysis products, today announced the addition of Jonathan Silverstein, General Partner of OrbiMed Advisors, LLC, (OrbiMed), to its Board of Directors. NxStage elected a representative from OrbiMed to its Board in connection with the recently announced private placement. The appointment of Mr. Silverstein fills a current vacancy on the Board and brings the number of members on NxStage’s Board to eight.

NxStage is pioneering a market with disruptive and innovative technology that is designed to dramatically improve the quality of life for patients with ESRD (end-stage renal disease), stated Jonathan Silverstein. I’m excited to join the team and to help NxStage achieve its strategic initiatives.

Jonathan brings extensive industry insight and expertise within the medical device and biotechnology markets, said Jeff Burbank, Chief Executive Officer of NxStage Medical. We believe that NxStage will significantly benefit from Jonathan’s experiences and we look forward to working with him as we continue to build value for all our shareholders.

Mr. Silverstein is General Partner at OrbiMed, an asset management firm solely focused in healthcare with several billion in assets under management. Mr. Silverstein joined OrbiMed in 1998 to focus on private equity investments and structured transactions of small-capitalization public biotechnology and medical device companies. Prior to joining OrbiMed, Mr. Silverstein was the Director of Life Sciences in the Investment Banking Department at Sumitomo Bank. Currently, Mr. Silverstein is the Chairman of Cerapedics, Gelesis and Enobia, and a director of superDimension, Ltd. He has been a former director or observer in an additional dozen companies including: Insulet Corporation (PODD), LifeCell (sold to KCI), Given Imaging (GIVN), Cerexa (sold to Forest Labs), Peninsula Pharmaceuticals (sold to Johnson & Johnson), Predix (sold to EPIX), Avanir (AVNR), Orthovita (VITA), Auxillium (AUXL), Bioenvision (sold to Genzyme), Adiana (sold to Cytyc), and Emphasys Medical. Mr. Silverstein has a B.A. in Economics from Denison University and a J.D. and M.B.A. from the University of San Diego.

About NxStage Medical

NxStage Medical, Inc. (Nasdaq: NXTM) is a medical device company, headquartered in Lawrence, Massachusetts, USA, that develops, manufactures and markets innovative products for the treatment of ESRD and acute kidney failure. For more information on NxStage and its products, please visit the company’s website at http://www.nxstage.com.

Forward-Looking Statements

This release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this release that are not clearly historical in nature are forward-looking, and the words anticipate, believe, expect, estimate, plan, and similar expressions are generally intended to identify forward-looking statements. Examples of these forward-looking statements include statements as to the contributions Mr. Silverstein will make to the company’s performance and operating results, the anticipated benefits of the company’s products, and the future growth of the company. All forward-looking statements involve risks, uncertainties and contingencies, many of which are beyond NxStage’s control, which may cause actual results, performance, or achievements to differ materially from anticipated results, performance or achievements. Certain factors which may affect future operating results are detailed in NxStage’s filings with the Securities and Exchange Commission, including the Quarterly Report on Form 10-Q for the period ending March 31, 2008. In addition, the statements in this press release represent NxStage’s expectations and beliefs as of the date of this press release. NxStage anticipates that subsequent events and developments may cause these expectations and beliefs to change. However, while NxStage may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so, whether as a result of new information, future events, or otherwise. These forward-looking statements should not be relied upon as representing NxStage’s expectations or beliefs as of any date subsequent to the date of this press release.

Important Additional Information

A special meeting of NxStage stockholders will be held on Thursday, July 31, 2008 to obtain stockholder approval for the second closing of a $43 million private placement in NxStage. In connection with the private placement and required stockholder approval, NxStage filed with the SEC a definitive proxy statement on July 8, 2008. This proxy statement was mailed to NxStage’s stockholders on or about July 9, 2008. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE PROXY STATEMENT AND OTHER RELEVANT DOCUMENTS FILED WITH THE SEC BECAUSE THEY CONTAIN IMPORTANT INFORMATION ABOUT NXSTAGE AND THE PRIVATE PLACEMENT. Investors and security holders may obtain free copies of these documents and other documents filed with the SEC at the SEC’s website at http://www.sec.gov, at NxStage’s website at http://www.nxstage.com or by writing to NxStage Medical, Inc., 439 S. Union St., 5th Floor, Lawrence, Massachusetts 01843, Attention: Investor Relations.

NxStage, its directors and the affiliates of its directors may be deemed to be participants in the solicitation of proxies with respect to the private placement. A description of the interests in NxStage of its directors, officers and such affiliates is set forth in NxStage’s proxy statement for its 2008 annual meeting of stockholders, filed with the SEC on April 29, 2008, and is included in the definitive proxy statement relating to the private placement and required stockholder approval filed with the SEC on July 8, 2008. These documents are available free of charge as described above.

Contact:

Kristen K. Sheppard, Esq.
VP, Investor Relations
ksheppard@nxstage.com

SOURCE NxStage Medical, Inc.

Web site: http://www.nxstage.com