A composite membrane consisting of three-dimensionally ordered macroporous (3DOM) silica matrix and sulfonated poly (1,4-phenylene ether ether sulfone) (SPEES) was prepared. Both water uptake and methanol permeability of the composite membrane changed according to the filling ratio of SPEES in the 3DOM silica matrix. Proton conductivity of the composite membrane was hardly influenced by the filling ratio, which was 6.0-6.5 X 10(-2) S cm(-1) at a filling ratio of 14-46%. This may be explained by the interface region between SPEES and silica having a high transfer of protons. Hence, the membrane having high proton conductivity and low methanol permeability was prepared by adjusting the filling ratio of SPEES. The prepared membrane has more than two times higher performance than Nafion as solid electrolyte membrane for direct methanol fuel cells. (c) 2007 The Electrochemical Society.