NxStage Medical, Inc.

In connection with the acquisition of NxStage Medical, Inc. by Fresenius Medical Care Holdings, Inc., Computershare Trust Company, N.A. has been retained as paying agent to manage the exchange of NxStage common stock for the merger consideration of $30.00 per share, without interest.  If you are a holder of shares of NxStage common stock represented by stock certificates and have any questions relating to the exchange process, please contact Computershare toll free at +1 (800) 546-5141 or outside the United States at +1 (781) 575-2765.  If your shares are held in “street name” by a broker, bank or other nominee, please contact that broker, bank or other nominee.