Proton conducting membranes are the most crucial part of energy generating electro-chemical systems such as polymer electrolyte membrane fuel cells (PEMFCs). in this work, Nafion based proton conducting anhydrous composite membranes were prepared via two different approaches. In the first, commercial Nafion115 and Nafion112 were swelled in the concentrated solution of azoles such as 1H-1,2,4-triazole (Tri), 3-amino-1, 2,4-triazole (ATri) and 5-aminotetrazole (ATet) as heterocyclic protogenic solvents. In the second, the proton conducting films were cast from the Nafion/Azole solutions. The partial protonation of azoles in the anhydrous membranes were studied by Fourier transform infrared (FT-IR) spectroscopy. Thermal properties were investigated via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA results showed that Nafion/ATri and Nafion/ATet electrolytes are thermally stable at least up to 200 degrees C. Methanol,permeability measurements showed that the composite membranes have lower methanol permeability compared to Nafion112. Nafion115/ATri system has better conductivity at 180 degrees C, exceeding 10(-3) S/cm compared to other Nafion/heterocycle systems under anhydrous conditions. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.