Platinum-cobalt nanoparticles were prepared from water/Triton X-100/propanol-2/cyclohexane reverse microemulsions. The Pt:Co ratio in the nanoparticles was well controlled by the initial concentrations of Pt and Co in the precursor solution. The nanoparticles were characterized by transmission electron microscopy, X-ray diffractometry and energy dispersive X-ray analysis. The Pt-Co nanoparticles supported on a carbon electrode possessed high dispersion and high catalytic activity for methanol oxidation in alkaline solution at room temperature. The optimum Pt:Co ratio for methanol oxidation was determined to be 1:0.5. (C) 2004 Elsevier B.V. All rights reserved.