Synthesis of single-walled carbon nanotube-supported platinum (Pt/SWNT) electrocatalyst using a rapid, one-step reduction of an aqueous ptCl(4)(2-) solution by methanol is reported. Pt nanoparticles are deposited onto SWNTs within 30 min of vigorous stirring with a small amount of methanol. Efficiency of this synthetic method is as high as 98%, and the mass of the Pt nanoparticles deposited on SWNTs is directly proportional to the initial concentration of the metal ion. Cyclic voltammetric analysis indicates excellent catalytic activity of the Pt/SWNT catalyst for methanol oxidation, with a peak current that is 2.5 times larger than a commercial Pt carbon black catalyst. The Pt/SWNT catalyst also exhibits significantly better activity with respect to oxygen reduction in comparison to the commercial Pt catalyst.