A novel deposition method of Pt catalysts onto Nafion membranes impregnated with polypyrrole (PPy) has been proposed for PEMFC application. The proton conductivity and water uptake of the chemically prepared PPy/Nafion composites were investigated. Even if polypyrrole had been combined with Nation, PPy/Nafion membrane retained cation exchange property similar to polypyrrole film doped with large anion like Nation solution. When Pt particle was deposited on PPy/Nafion composites, the Pt loading yeild and the activity surface area were enhanced with polymerization time of pyrrole. The performance evaluation with membrane electrode assembly composed of Pt/PPy/Nafion composite and diffusion electrode was carried out using a single cell. As a result of fuel cell test, current density of 888 mA/cm(2) at 0.3 V has been observed for MEA contained with Pt/PPy/Nafion composite. (C) 2004 Elsevier Ltd. All rights reserved.