Electrocatalytic activity of Pr alloys with Ni, Co, and Fe, formed by sputtering, was investigated with regard to the oxygen reduction reaction (ORR) in perchloric acid solution. Hydrodynamic voltammograms with rotated electrodes were used to measure the electrocatalytic activity. Maximum activity was observed at ca. 30, 40, and 50% content of Ni, Co, and Fe, respectively, by which 10, 15, and 20 times larger kinetic current densities than that of purr Pt were attained, X-ray photoelectron spectroscopy analysis of the surfaces after the reaction indicated that the active surfaces were covered by a few monolayers of Pt. We present an enhancing mechanism for the ORR based on an increased d-electron vacancy of the thin Pt surface layer caused by underlying alloy. Result!, of this work contribute in development of new active cathode catalysts fur fuel cells used as power sources of electric vehicles, etc.