The synthesis, physical characterization, decontamination and some electrocatalytic properties of PtRu nanoparticles prepared using the microemulsion method are reported. The nanoparticles are synthesized by reduction with sodium borohydride of H2PtCl6 and RuCl3 in a water-in-oil microemulsion of water/polyethylenglycol-dodecylether (BRIJ(R)30)/n-heptane. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive analysis by X-rays (EDAX) experiments were carried out to characterize the single and bimetallic nanoparticles obtained. Cyclic voltammograms (CV) of clean nanoparticles were obtained after a controlled decontamination procedure of their surfaces. CO adsorption-oxidation and methanol electrooxidation were used as test reactions to check the electrocatalytic behaviour of the bimetallic nanoparticles. Pt80Ru20 (nominal atomic composition) nanoparticles are the best electrocatalyst for both COad and methanol oxidation. All these results show that the microemulsion method can be used to produce bimetallic nanoparticles in a very easy way. The method can be very easily scaled-up for industrial use. (C) 2004 Elsevier Ltd. All rights reserved.