Carbon-supported PtTi alloy nanoparticles with well-controlled particle size, dispersity, and composition uniformity, have been synthesized by thermal decomposition and reduction of Pt and Ti precursors at elevated temperatures. The synthesized alloy nanoparticles were characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive spectroscopy. The catalytic activities of these alloys towards molecular oxygen electro-reduction were screened by the hydrodynamic RDE technique. Among the compositions tested, Pt75Ti25 displayed the highest catalytic activity and had a twofold improvement in catalytic performance as compared to a benchmark Pt/C catalyst. (C) 2007 Elsevier B.V. All rights reserved.