Pt nanoparticles supported on multi-walled carbon nanotubes (MWNTs) were obtained by gamma-irradiation induced synthesis and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Pt nanoparticles, which were uniform in shape and size and well dispersed on the carbon nanotubes, were 2.5-4.0 nm in diameter. Test runs on a single stack proton exchange membrane fuel cell (PEMFC) showed that these electrocatalysts are very promising for fuel cell applications. (c) 2006 Elsevier B.V. All rights reserved.