Unsupported PtRu alloy powders of a wide range of compositions were prepared at low temperatures by carefully adjusting the preparation procedure. PtRu alloys of essentially the same surface, nominal and bulk composition, were formed up to ca. 46 atom % Ru content. Adsorbed CO stripping voltammetry and CH3OH oxidation characteristics, namely, i-V curves and pseudo-steady-state current density values recorded at constant potentials, were the same as reported for corresponding bulk alloys, suggesting that the electrocatalytic activities of the powders can be compared to bulk alloys. CH3OH oxidation activities obtained for PtRu alloy, Pt, and Ru powders showed the PtRu alloy of 70: 30 atom % Pt: Ru composition to exhibit the highest activity independent of the temperature and potential tested (0.3 and 0.4 V vs. a reversible hydrogen electrode). The experimental pseudo-steady-state current density values for the CH3OH oxidation reaction were found to show the same dependence on Ru content as theoretical values calculated assuming that an assembly of three neighboring Pt and one Ru site are involved in the oxidation of a CH3OH molecule. (C) 2004 The Electrochemical Society.