Related Party Transactions and Outside Related Director Information

NxStage Medical, Inc. (NXTM)

4/28/2006 Proxy Information

Medisystems Corporation Medisystems Corporation is our primary supplier of the disposable cartridges used with our NxStage System One and our only supplier of cartridge subassemblies. The chief executive officer and sole stockholder of Medisystems, David S. Utterberg, is a member of our Board of Directors and owns approximately 9.4% of our outstanding common stock. We purchased approximately $896,000 of products during fiscal 2005 from Medisystems. We are currently negotiating a long-term supply agreement with Medisystems covering components, subassemblies and completed cartridges, and are hopeful that we will be able to complete our negotiations and enter into a definitive agreement with Medisystems in the near term. We believe that our purchases from Medisystems have been on terms no less favorable to us than could be obtained from unaffiliated third parties. Registration Rights The following directors, officers and holders of more than five percent of our voting securities and their affiliates have been granted registration rights with respect to shares of our common stock: (See page 24 of proxy for table).