NxStage to Report Second Quarter 2008 Financial Results on Tuesday, August 5, 2008

Thursday July 17, 2008

LAWRENCE, Mass., July 17 /PRNewswire-FirstCall/ — NxStage Medical, Inc. (Nasdaq: NXTM), a leading manufacturer of innovative dialysis products, today announced plans to release its financial results for the second quarter ended June 30, 2008, on Tuesday, August 5, 2008 before the opening of the financial markets.

NxStage will also host a conference call at 9:00 a.m. Eastern Time on Tuesday, August 5, 2008 to discuss its second quarter financial results. To listen to the conference call, please dial 800-901-5248 (domestic) or 617-786- 4512 (international). The passcode is 34533100. The call will also be webcast LIVE and can be accessed via the investor relations section of the website at www.nxstage.com/ir.cfm .

A replay of the conference call will be available 2 hours after the start of the call through August 19, 2008. To access the replay dial 888-286-8010 (domestic) or 617-801-6888 (international), and enter passcode 62216803. An online archive of the conference call can be accessed via the investor relations section of the website at www.nxstage.com/ir.cfm .

About NxStage

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 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. The forward-looking statements in this release include NxStage’s plan to release its financial results on August 5, 2008. Actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors including, but not limited to, unexpected difficulty in closing the company’s financial books for the quarter and other factors that are discussed in NxStage’s Quarterly Report on Form 10- Q for the period ended March 31, 2008 filed with the SEC. NxStage is under no obligation to (and expressly disclaims any such obligation to) update or alter its forward-looking statements, whether as a result of new information, future events or otherwise.

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 www.sec.gov, at NxStage’s website at 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