Nafion 117 was coated with thin layers of metallic Pd by electroless deposition from commercial plating baths. The deposits were well adhering and crack-free. In a purpose-built direct methanol fuel cell for liquid electrolyte, the methanol-blocking ability of the Nafion/Pd composites was studied. The cell construction allowed determining the methanol concentration directly in the catholyte while recording electrochemical parameters. Compared to bare Nation, the Nafion/Pd composites considerably reduced methanol crossover. This resulted in enhanced cell performance, which was found to be somewhat dependent also on the potential of the Pd layer. (C) 2004 Elsevier B.V. All rights reserved.