A new polymer electrolyte membrane prepared by radiation grafting of vinyltoluene into poly(ethylene-co-tetrafluoroethylene) (ETFE) film and subsequent sulfonation was developed for application in fuel cells. The effect of grafting condition on the degree of grafting was investigated in detail. Results indicated that the degree of grafting can be controlled over a wide range. The grafted films were sulfonated in a chlorosulfonic acid solution to obtain the polymer electrolyte membranes, which were characterized with respect to their use in fuel cells. It is concluded that the substituted methyl group on the vinyltoluene can improve the chemical stability of the resulting membranes, and the crosslinked ETFE-g-poly(vinyltolueneco-clivinylbenzene) membranes can be proposed for the future development of alternative low-cost and high-performance membranes for fuel cells. (c) 2006 Wiley Periodicals, Inc.