Carbon-supported Pt-Co and Pt catalysts are prepared by NaBH4 reduction of metal precursors. The particles size of Pt-Co varies with the pH used in the preparation, it is largest (12 nm) in alkaline solution and smallest (3.7 nm) in un-buffered solution. For the latter, X-ray photoelectron spectroscopy shows that Pt exists principally in the metallic state, whereas cobalt is mostly oxidized. The performance of the catalysts for methanol electro-oxidation in acidic media at room temperature is evaluated and compared with that of a Pt/C catalyst. Electrochemical measurements by cyclic voltammetry and chronoamperometry demonstrate consistently high catalytic activities and improved resistance to carbon monoxide for the Pt-Co catalysts, particularly for that prepared in un-buffered solution. (C) 2004 Elsevier B.V. All rights reserved.