The kinetics of the reduction of oxygen at the surface of a platinum disc covered with thin layers of polymer has been studied in 0.5 M H2SO4 at ambient temperature in order to establish to what extent the polymer affects the reaction mechanism. Experiments were performed particularly to determine the oxygen permeability DfCf (product of the diffusion coefficient and the oxygen concentration in the film) for Nation (R) and other polymers such as sulfonated polyimide (PIS), sulfonated polyetherketone (PEEKs) and non-sulfonated polybenzimidazole (PBI). The product DfCf depends on the nature of the polymer. Furthermore, how well the active layer works depends markedly on the amount of polymer it contains. (c) 2005 Elsevier B.V. All rights reserved.