The introduction of different percentages of H-BETA zeolite, as an inorganic filler, into the S-polyetheretherketone (S-PEEK) membrane was investigated. For the good thermal stability, a sulphonation degree of about 50% was chosen for the bare S-PEEK. The obtained membranes were studied in terms of chemical-physical and electrochemical properties. The introduction of zeolite produces a strong reduction of the swelling with respect to the bare S-PEEK membrane without decreasing the proton conductivity. The benefit of the zeolite introduction is confirmed by the electrochemical tests, reaching higher performance than bare S-PEEK membrane at temperature over 100 degrees C. Composite electrodes with different percentages of zeolite in the catalytic layer were developed to improve the water management at T > 100 degrees C. A composite MEA, obtained by assembling the best composite membrane and electrodes, was produced and characterised in terms of I-V curve at 120 degrees C reaching a maximum power density of about 310 MW cm(-2). (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.