The effect of the type of carbon support on the catalytic activity of Pt-Ru/C catalysts for methanol oxidation in direct methanol fuel cells (DMFCs) was investigated. The morphological and structural properties of high surface area (>200 m(2) g(-1)) carbon powders and such electrochemical parameters of carbon-Nafion composites as accessible surface area and electric resistance are related to the structure, morphology, and catalytic activity of Pt-Ru catalysts electrochemically prepared on carbon-Nafion supports. Key data are reported, discussed, and compared to those obtained with a commercial Pt-Ru/C catalyst. (C) 2004 The Electrochemical Society.