X0303 4 2010-12-17 0 0001333170 NxStage Medical, Inc. NXTM 0001429894 Shea Thomas C/O NXSTAGE MEDICAL, INC. 439 SOUTH UNION STREET LAWRENCE MA 01843 0 1 0 0 SVP Manufacturing Operations Common Stock 2010-12-17 4 M 0 1000 2.11 A 45310 D Common Stock 2010-12-17 4 S 0 1000 23.509 D 44310 D Stock Option (right to buy) 2.11 2010-12-17 4 M 0 1000 0.00 D 2009-04-05 2016-03-04 Common Stock 1000 49000 D This sale was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 15, 2010. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $23.50 to $23.52. The reporting person undertakes to provide to the issuer, any holder of the issuer's stock, or the SEC, upon request, full information regarding the number of shares sold at each separate price within the range described above. This option was granted on March 5, 2009 and vests over three years in equal monthly installments. /s/ Winifred L. Swan, attorney-in-fact 2010-12-17