Fullerene composite membranes have been prepared by doping Nafion((R)) 117 with fullerenes to fabricate proton conducting composite membranes. The fullerenes used for the composites included C-60 and polyhydroxy fullerene, C-60(OH), (n similar to 12). We report the preparation and the characterization of the composites. ac impedance measurements have indicated that the fullerene-Nafion((R)) composite membranes have higher proton conductivities at both 20 and 80 degrees C than Nafion((R)) 117, especially under low relative humidity, < 50% RH. It has been found from water uptake measurements under 25% relative humidity that the fullerene-Nafion((R)) composite held more water than Nation((R)) 117 under low humidity. Molecular modeling of the fullerenes support the experimental observations. (c) 2006 Elsevier B.V. All rights reserved.