Carbon-supported Pt-Ni electrocatalysts in the Pt:Ni atomic ratio 90:10 and 70:30 were prepared by reduction at room temperature of Pt and Ni salts with sodium borohydride and tested for the first time in direct methanol fuel cells (DMFCs) both as anode and as cathode materials. The performance of Pt-Ni as cathode in DMFC was higher than that of Pt-Ni as anode. Pt90Ni10 as cathode showed better performance than Pt both in terms of mass activity and specific activity. When used as an anode material, the cell performance increased with increasing nickel content in the material. The enhanced performance of Pt-Ni as a cathode is ascribed both to a better activity for the oxygen reduction (electronic effect) and a better methanol-tolerance (ensemble effect) than Pt, related mainly to the alloyed nickel, while the improvement of Pt-Ni as anode for methanol oxidation is attributed to the presence of nonalloyed NiO species. (C) 2005 The Electrochemical Society.