Through sol-gel reactions, a series of sulfonated poly(ether ether ketone) (SPEEK)/TiO2 hybrid membranes with various contents of nano-sized TiO2 particles were prepared and characterized. It was found that with the increasing of the TiO2 contents in the hybrid membranes, the water uptake and water retention increased. Meanwhile, the introduction of inorganic particles reduced the methanol permeability. The proton conductivity was enhanced by introduction of hydrophilic inorganic particles into the SPEEK membranes, which might be an effective approach to increase the working temperature of PEM. (C) 2008 Wiley Periodicals, Inc.