HERA-B RICH: Performance and physics impact

The HERA-B RICH has been in operation between 1998 and 2003 with excellent stability. The counter, which employed multi anode PMTs as photon detectors, successfully operated in a hostile environment of a hadron machine. It allowed for reliable separation of kaons and pions in the momentum range between 5 and 50GeV/c. We report on its performance and its impact on the physics analysis of the measured data.