Pt/C, Pt-Ru/C and Pt-Mo/C electrocatalysts are used for hydrogen oxidation in polymer electrolyte fuel cells (PEFGs). In this paper, we report a semi-empirical equation that fits experimental electrode potential versus current density data for gas diffusion anodes using these electrocatalysts. The physico-chemical interpretation of all parameters used in the equation is also given. The presence of a strong kinetic limitation on Pt-M/C (M = Ru or Mo) electrodes is demonstrated. A Heyrowsky-Volmer mechanism for the hydrogen oxidation reaction is proposed on Pt-Mo/C and Pt-Ru/C. Accurate analysis of the cell voltage Versus current density plots of polymer electrolyte fuel cells with Pt-Mo/C anodes show that it is difficult to evaluate the best Pt/Mo atomic ratio from full-cell measurements, while half-cell data are more useful for kinetic studies. (C) 2000 Elsevier Science Ltd. All rights reserved.