Nanoporous anatase thin films (see Figure) have been prepared via particulate sol-gel processes. The proton conductivity shows a sigmoidal dependence on relative humidity (RH). The highest value of proton conductivity was 3.78 x 10(-2) S cm(-1) at 80 degrees C and 81 % RH. The comparable proton conductivity, lower cost, and higher hydrophilicity of these thin films make them potential substitutes for Nafion membranes in proton-exchange membrane fuel cells.