The present work uses cyclic voltammetry, electrochemical impedance technique and potentiostatic current transient technique to investigate hydrogen transport through an anodic WO3 film subjected to the impermeable constraint in 0.1 M H2SO4 solution. From the experimental results, it is inferred that the reversibility of hydrogen transport through the anodic crystalline WO3 film during later cycles is raised as a result of the number of irreversible trap sites in the him being filled with hydrogen, which increase during the early cycles. It is confirmed that the anodic crystalline WO3 films, containing water, permit more favorable hydrogen transport than the water-free r.f.-magnetron-sputtered crystalline WO3 films. With the help of the results of simulation of the potentiostatic current transients with varying initial concentration in the electrode, based upon a diffusion equation involving stress-induced diffusion, the results of the potentiostatic current transient experimentally obtained are satisfactorily analyzed. The stress developed during hydrogen injection or extraction is divided into the enhancing and retarding contributions to the hydrogen transport through the film. (C) 1998 Elsevier Science Ltd. All rights reserved.