NxStage(R) Medical and DaVita Announce Agreement for Home Hemodialysis Using the NxStage System One(TM)

Wednesday February 7, 2007

LAWRENCE, Mass., Feb. 7 /PRNewswire-FirstCall/ — NxStage Medical, Inc. (Nasdaq: NXTM), the manufacturer of the NxStage System One&#153 portable kidney dialysis machine, today announced a multi-year, national agreement with certain market rights, under which the two companies will collaborate on expanding availability of home hemodialysis to patients across the continental United States. DaVita has purchased $20 million in NxStage stock at a price of $10 per share, representing an ownership position of approximately 7%.

As part of the agreement, DaVita has purchased outright all of its System One equipment currently in use for approximately $5 million, and will purchase the majority of its future home hemodialysis equipment requirements. Additionally, the companies have agreed to collaborate on a variety of initiatives to expand the home hemodialysis market such as public awareness, public policy and additional research efforts.

We are pleased to expand our relationship with DaVita, said Jeffrey H. Burbank, President & CEO of NxStage Medical. The last year has been a pivotal one for home hemodialysis and we are grateful to all of our partners, including DaVita, for demonstrating a commitment to this treatment modality. With this partnership, we are furthering our company’s strategy of working with a select group of passionate providers in each geography in order to increase patient access to home therapy.

We are excited about the opportunity this partnership offers our patients, stated Kent Thiry, CEO of DaVita. Providing our patients with a variety of dialysis options, either in-center or at home, is consistent with our mission to be the provider of choice for dialysis patients.

The NxStage System One is the first truly portable hemodialysis system cleared for home use by the FDA. Unlike traditional dialysis equipment, the System One plugs into standard electrical outlets, requires no special infrastructure to operate and is easy to use by trained patients accompanied by their trained partners. Patients who use the NxStage System One have the personal freedom to conduct prescribed treatments at home on their own schedule and more frequently. An additional benefit of the System One is the ability to travel with it.

Conference Call

NxStage will host a conference call to discuss this announcement at 6:30 PM Eastern Time this evening, February 7, 2007. To listen to the conference call, please dial (800) 299-9630 for domestic callers and (617) 786-2904 for international callers. The passcode is 26421856. A replay of the conference call will be available through February 21, 2007 by dialing (888) 286-8010 (domestic) and (617) 801-6888 (international), passcode 29388813. An online archive of the conference call will also be available by accessing the Investor Relations section of the company’s website at www.nxstage.com.

About End-Stage Renal Disease:

End-stage renal disease is the permanent failure of the kidneys to filter the body’s wastes. It is most commonly caused by diabetes, hypertension or genetic disorders. In order to survive, ESRD patients must use some form of therapy to replace the function of the kidneys for the rest of their lives. Currently, over 450,000 patients in the United States suffer from ESRD, and the costs of treating ESRD patients are more than $20 billion annually in the United States. Due to increases in diabetes, hypertension and the aging of the U.S. population, those figures are projected to double within the next 10- 15 years. The most common form of kidney replacement therapy in the United States today is hemodialysis, which is used by over 350,000 patients currently. The great majority of these patients are treated with conventional, in-center hemodialysis, in which they must travel to a nearby dialysis center three times per week, where they are connected to dialysis machines for treatments lasting approximately three to four hours, to cleanse their blood.

About Hemodialysis:

Today, most patients undergo hemodialysis therapy three times a week in outpatient dialysis centers. This differs significantly from the 24/7 workings of the naturally functioning kidney. Increasingly, clinicians and patients have recognized opportunities for therapy improvements with more frequent, or daily, dialysis. More than a hundred clinical papers have reported on the health and quality of life benefits of hemodialysis done more frequently. The reported benefits include reduced hypertension, reduced cardiac strain and left ventricular hypertrophy, reduced amyloid disease, and improved anemia status, appetite, and quality of life, including the ability to return to work.

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 anticipated demand for home and or daily dialysis products, the anticipated market acceptance and demand for NxStage’s products, and anticipated increases in availability of and market and patient awareness regarding home hemodialysis. 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 including risks related to growth in home or more frequent hemodialysis, market acceptance and demand for NxStage’s products and certain other factors that may affect future operating results and which are detailed in NxStage’s filings with the Securities and Exchange Commission, including the Quarterly Report on Form 10-Q for the three months ended September 30, 2006.

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.

About NxStage Medical:

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

SOURCE NxStage Medical, Inc.

Contact:
Kristen K. Sheppard, Esq.
Vice President, Investor Relations
NxStage Medical Inc. (NXTM)
978/332-5923
Web site: http://www.nxstage.com