Solution cast composite direct methanol fuel cell membranes (DEZ) based on DE2020 Nafion (R) dispersion and in-house prepared H-ZSM-5 zeolites with different Si/Al ratios were prepared and thoroughly characterized for direct methanol fuel cell (DMFC) applications. All composite membranes have indeed lower methanol permeability and higher proton conductivity than pure DE2020 membrane. The composite membranes with Si/Al ratio 25 and 5 wt.% of zeolites (DEZ25-5) having the lowest methanol permeability and the membrane with Si/Al ratio 50 and I wt.% of zeolites (DEZ50-1) having the highest proton conductivity were tested in the DMFC for several days. The DEZ25-5 has the best performance; namely high power density and stable performance in time. (C) 2009 Elsevier B.V. All rights reserved.