The synthesis of carbon-supported unalloyed Au-Pt bimetallic nanoparticles using polyol method at a temperature as low as 85 degrees C is reported. Various compositions of Au-Pt/C bimetallic nanoparticles are characterized using transmission electron microscopy (TEM), X-ray florescence (XRF), X-ray diffraction and cyclic voltammetry. Electron microscopy shows that the particles have a near-narrow size distribution that peaks at an average size of similar to 5 to 6 nm. The electrocatalytic activity of Au-Pt/C nanoparticles, towards the oxygen reduction reaction (ORR) is studied by linear sweep polarization measurements obtained using a rotating disc electrode (RDE). The results reveal that a four-electron transfer pathway is mainly operative for ORR and the half-wave potential for ORR on bimetallic Au-Pt/C (20%:20%) is similar to 100 mV less negative when compared with that of Pt/C (home-made and E-Tek). Studies of the methanol oxidation reaction (MOR) on these catalysts show that the MOR activity is significantly lowered with increasing content of Au in Au-Pt/C. (c) 2008 Elsevier B.V. All rights reserved.