The kinetics of oxygen reduction (ORR) on carbon cryogel supported Pt nanoparticles (Pt / C) in acid solution was studied using the rotating disk electrode technique. This electrocatalyst was prepared by a modified polyol synthesis method and characterized by transmission electron microscopies. The kinetics of ORR shows a significant enhancement at Pt nanoparticle surfaces as compared with the same reaction on polycrystalline Pt surface. The four-electron reduction, with a first-charge transfer-rate determining step, has been found to be operative. However, the specific activity of the Pt / C is similar to that of the polycrystalline Pt electrocatalyst.