NxStage(R) Medical to Report Fourth Quarter & Full Year 2006 Financial Results on Thursday, February 15th

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, announced plans to release its financial results for the fourth quarter and full year ended December 31, 2006 on Thursday, February 15, 2007 before the opening of the financial markets.

NxStage will also host a conference call at 9:00 a.m. Eastern Time on February 15, 2007 to discuss its fourth quarter and year end 2006 financial results. To listen to the conference call, please dial (866) 711-8198 for domestic callers and (617) 597-5327 for international callers. The passcode is 53954494. A replay of the conference call will be available two hours after the start of the call through February 22, 2007 by dialing 888-286-8010 (domestic) and 617-801-6888 (international), passcode 88520622. An online archive of the conference call will also be available by accessing the Investor Information section of the company’s website at www.nxstage.com.

About NxStage Medical

NxStage Medical, Inc. is a medical device company, headquartered in Lawrence, Massachusetts, USA, that develops, manufactures and markets innovative 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.

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 February 15, 2007. 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 quarter ended September 30, 2006 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.

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