Composite Nafion-based membranes, containing 5 wt % of high-purity mesoporous titania with an average pore size of about 3.5 nm heated to 350, 450, and 600 degrees C as a filler were successfully recasted. Field emission scanning electron microscopy observations showed a high degree of dispersion of mesoporous titania particles in Nafion. Direct methanol fuel cell investigation of such membranes at temperatures higher than 100 degrees C revealed a considerable influence of the presence of the ceramic oxide and of its specific surface area on the electrochemical behavior. The composite membranes allowed operation up to 145 degrees C, showing a significant performance improvement with respect to pure Nafion. At 145 degrees C with oxygen feed, a power density of about 335 mW/cm(2) was recorded for the composite Nafion-based membranes, containing 5 wt % of mesoporous titania calcined at 450 degrees C. (c) 2005 The Electrochemical Society. All rights reserved.