A Pt-C/sulfonated poly(ether ether ketone)/polytetrafluoroethylene (Pt-C/SPEEK/PTFE) self-humidifying composite membrane for the H-2/O-2 fuel cell was developed. Compared with the performance of the cells prepared with SPEEK/PTFE composite membranes, the performance with the self-humidifying composite membranes was appreciably improved when holding the humidity of cathode gas constant. The Pt-C/SPEEK/PTFE composite membrane can supply water to the anode electrode side under dry H-2 condition and result in good cell performance. (C) 2004 The Electrochemical Society.