X0202 4 2007-03-30 0 0001333170 NxStage Medical, Inc. NXTM 0001162977 REID PERPER C/O NXSTAGE MEDICAL, INC. 439 SOUTH UNION STREET, 5TH FLOOR LAWRENCE MA 01843 1 0 0 0 Common Stock 2007-03-30 4 A 0 1482 0.00 A 1280524 D Pursuant to the issuer's director compensation policy, non-employee directors may elect to receive shares of the issuer's common stock in lieu of cash compensation payable pursuant to such policy. Payments of common stock in lieu of cash compensation are made quarterly in the amount of the total cash compensation earned by a non-employee director during such quarter divided by the closing price of the issuer's common stock on the last day of the quarter. The closing price of the issuer's common stock on March 30, 2007 was $13.32. Includes 1,276,112 shares owned directly by Healthcare Investment Partners Holdings LLC, or HIP. Reid Perper, in his capacity as a Managing Partner of HIP, may be deemed to beneficially own these shares. Mr. Perper disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein. /s/ Winifred L. Swan, as attorney-in-fact 2007-04-06