The influences of the Nation film thickness and Pt loading on the kinetics of the hydrogen oxidation reaction on Nafion-coated 20 wt% Pt/C electrodes immersed in 0.5 M H2SO4 were investigated using a rotating disk electrode configuration. The coating of a Nafion film (<= 8 mu m) had a negligible effect on the electrochemical surface area of an electrode. The kinetic parameters were estimated at an overpotential of 0.4 V; the values obtained were shown to vary with the method of data treatment. The diffusional resistance for H-2 in the Nafion film was negligible when the film was thinner than 0.2 mu m. The permeability of H2 in the Nafion film ranged from 2.4 x 10(-5) to 4.8 x 10(-5) mM cm(2)/s. The error analysis demonstrated that the apparent kinetic current estimated was resulted from experimental errors, instead of resulting from a chemical process as proposed by some previous investigators. (C) 2007 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.