In this work we report the synthesis of proton-conducting gel membranes＇ obtained by incorporating salicylic acid in a highly plasticized (poly)methylmethacrylate matrix. We have prepared these gel membranes by using particular solvent mixtures consisting of propylene carbonate (PC), ethylene carbonate (EC), and fixed molar ratios of either dimethylformamide (DMF), methylformamide (MF), or formamide (F). The conductivity of the gel membranes prepared from these three-solvent mixtures is higher than that obtained by the parent liquid PC/EC solutions. Furthermore,the membranes are stable at moderately high temperatures (not exceeding 70 degrees C), and their conductivity is only moderately dependent on the relative humidity conditions.