A one-step process is designed for the preparation of PtRu (1:1) electrocatalysts by the polyol method. Following investigations with an UV-vis spectrophotometer and an inductive-coupled plasma atomic emission spectrophotometer, it is found that an equimolar solution of Pt and Ru salts dissolved in ethylene glycol at temperatures above 190 C is essential for the formation of the PtRu (1:1) solid solution. X-ray diffraction analysis is used to characterize the composition and size of the prepared electrocatalysts. The lattice parameter is 3.8663 angstrom, which corresponds to the value for a PtRu solid solution of equiatomic composition and this atomic ratio is confirmed by energy dispersive X-ray spectroscopy. Based on the Scherrer formula, the average particle size of the electrocatalysts is estimated to be 2.6 nm. It is confirmed by transmission electron microscopy that the nanoparticles are distributed uniformly on carbon, Vulcan XC 72. According to the results of unit cell test and CO-stripping voltammetry, the performance of the prepared electrocatalyst is comparable with that of a commercial one of the same composition. (c) 2006 Elsevier B.V All rights reserved.