The synthesis and characterization of a novel hybrid organic-inorganic material formed by phosphomolybdic acid H3Mo12O40 (PMo12) and poly(2,5-benzimidazole) (ABPBI) is reported. This material, composed of two proton-conducting components, can be cast in the form of membranes from methanesulfonic acid (MSA) solutions. Upon impregnation with phosphoric acid, the hybrid membranes present higher conductivity than the best ABPBI polymer membranes impregnated in the same conditions. These electrolyte membranes are stable up to 200 degrees C, and have a proton conductivity of 3 x 10(-2) S cm(-1) at 185 degrees C without humidification. These properties make them very good candidates as membranes for polymer electrolyte membrane fuel cells (PEMFC) at temperatures of 100-200 degrees C. (C) 2005 Elsevier Ltd. All rights reserved.