Literature results concerning proton conducting polymer electrolytes are reviewed with emphasis on acid doped polymer blends and on derived systems obtained by adding an inorganic filler or a plasticizer or both. In addition, conductivity results are provided on anhydrous polyamide/H3PO4 blends in a wide acid concentration range and on new membranes involving a fluorinated polymer, silica and H3PO4 or H2SO4 aqueous solutions. The room temperature conductivity of 10(-1) S cm(-1) reached by these membranes is discussed using in situ Raman spectroscopy measurements of the acid concentration, General trends and prospects are tentatively drawn from the available results.