The nanocrystalline Pb-Ru pyrochlore prepared by reverse microemulsion method has been used as the cathode electro catalyst for oxygen reduction reaction in proton exchange membrane (Nafion 117) medium. The oxide particles prepared were found to have nanosized spherical as well as filament type particles. The nanocrystalline Pb-Ru pyrochlore was found to exhibit comparable electrocatalytic activity and stability with commercial platinum catalyst, for oxygen reduction reaction. (c) 2005 Springer Science + Business Media, Inc.