An acid-base polymer blend membrane based on sulphonated poly(etheretherketone) (SPEEK) and poly(benzimidazole) (PBI) was developed for direct methanol fuel cells. Thermal stability, water uptake, ion exchange capacity, conductivity and fuel cell performance of the membrane were studied and compared to that of nafion. The conductivity of nafion was found to be superior to SPEEK/PBI membrane; however, the thickness of SPEEK/PBI membranes can be reduced considerably. SPEEK/PBI membrane with a thickness of 55 mu m showed a significant improvement in the DMFC performance as compared to Nafion 117. The maximum power densities obtained with SPEEK/PBI membranes are twice better than. Nafion 117 at 60 degrees C. SPEEK/PBI membranes showed excellent stability under DMFC operating conditions up to 60 degrees C and therefore are seen as ideal candidates for portable DMFC applications. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.