A new approach to study the performance characteristics of the HERA-B RICH using momenta reconstructed with RICH track direction measurements is presented. The particle identification performance is found to meet design specifications: electron-pion separation for momenta up to 15 GeV/c, pion-kaon separation to 54 GeV/c. The normalized photo-electron yield is found to he 42 +/- 5 cm(-1) rad(-2) and the single-photon angular resolution is better than 0.7 mrad. (C) 2001 Elsevier Science B.V. All rights reserved.