In this work, carbon-supported Pt:Ru electrocatalysts, mainly for application in polymer electrolyte fuel cells, have been prepared by different methods. The materials were tested in single cells with respect to the hydrogen-oxidation reaction in the presence of CO, and the performances, before and after thermal treatments, compared to that of state-of-the-art, commercial E-TEK catalysts. In most cases, it was found that the performance of the anode improves substantially after the thermal treatment of the material. Of the several methods considered, the preparation of the catalyst via the formation of a sulfite complex, followed by a thermal treatment, gave the best results, comparable to those obtained with the state-of-the-art catalyst. (C) 2000 Elsevier Science S.A. All rights reserved.