This paper reviews the properties of a new microporous, composite proton-conducting gel membrane, formed by swelling with aqueous acid solutions suitable polymer matrices containing dispersed ceramic fillers. The data reported show that these membranes have a high and stable conductivity, a proton transport intrinsically provided by the absorbed acid solution not strictly influenced by the external humidity level, and a projected very low cost. Tests in a hydrogen-air laboratory cell also demonstrate that the membranes are basically suitable for application in polymer electrolyte fuel cells. (c) 2006 The Electrochemical Society.