Platinum nanoparticles on a conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), exhibit a high catalytic activity for electrooxidation of methanol. Pt nanoparticles are prepared by potentiostatic deposition in chloroplatinic acid solution at 0.1 V versus standard calomel electrode (SCE) on PEDOT coated carbon paper. PEDOT on the substrate facilitates the formation of uniform, well-dispersed, small clusters of Pt that consist of nanosize particles. The cyclic voltammogram of methanol oxidation is characterized by a forward oxidation peak current at 0.60 V vs SCE and a backward oxidation peak current at 0.50 V vs SCE. The mass specific peak current is found to be as high as 614 mA mg(-1), The effects of concentration of H2SO4, mass of Pt, and quantity of PEDOT on mass specific activity are studied.