The electrooxidation of hydrogen at platinum electrodes dispersed ih a polyaniline matrix with several platinum loadings (ranging from 5 to 327 mu g cm(-2)) was investigated using a rotating disc electrode. This allowed us to separate the different contributions (diffusion of molecular hydrogen, adsorption step, electron transfer step) in the overall oxidation process. The variation of the kinetic parameters (Tafel slope, exchange current density, limiting adsorption current) with the platinum loading was interpreted in terms of the different mechanisms usually postulated for the hydrogen oxidation reaction.