EXHIBIT 21.1

Subsidiaries of the Registrant

Name	Jurisdiction of Incorporation
EIR Medical, Inc. (100% owned by NxStage Medical Inc.)	Massachusetts
NxStage Verwaltungs GmbH (100% owned by EIR Medical, Inc.)	Germany
NxStage GmbH & Co. KG (100% of limited partnership interests owned by EIR Medical, Inc.; 100% of general partnership interests owned by NxStage Verwaltungs GmbH)	Germany
Medisystems Corporation (100% owned by NxStage Medical Inc.)	Washington
Medisystems Services Corporation (100% owned by NxStage Medical Inc.)	Nevada
Medimexico s. de R.L. de C.V. (100% owned by NxStage Medical Inc.)	Mexico
Medisystems Europe S.p.A (100% owned by NxStage Medical Inc.)	Italy
NxStage Medical UK Limited (100% owned by NxStage Medical Inc.)	United Kingdom