Nafion-silica composite membranes doped with phosphotungstic and silicotungstic acids have been investigated for application in direct methanol fuel cells at high temperature (145 degreesC). The phosphotungstic acid-based membrane showed better electrochemical characteristics at high current densities with respect to both silicotungstic acid-modified membrane and silica-Nafion membrane. A maximum power density of 400 mW cm(-2) was obtained at 145 degreesC in the presence of oxygen feed, whereas the maximum power density in the presence of air feed was approaching 250 mW cm(-2), The results indicate that the addition of inorganic hygroscopic materials to recast Nation extends the operating range of a direct methanol fuel cell. Operation at high temperatures significantly enhances the kinetics of methanol oxidation.