The permeation of hydrogen through palladium composite membranes was investigated at temperatures 523-669 K and hydrogen pressures 80-220 kPa. Two pieces of Pd/alpha-alumina composite membranes prepared by electroless deposition were used in this study. The permeation behavior of hydrogen through the palladium composite membranes was analyzed by a resistance model in order to obtain the permeation parameters of the support and palladium layer. The results demonstrated that the thickness of the Pd layer played an important role in the permeation properties of hydrogen. The hydrogen flux through a Pd/alumina composite membrane, with a palladium film of 7 mum thickness, deviated from Sievert's law. This was due to decreasing the thickness of the Pd film, resulting in a significant surface limiting process contribution. In addition, Sievert's law was in good agreement with the data obtained for thick Pd film (15 mum), and it provided accurate prediction of permeability coefficient, activation energy, and the values of Delta H H 0 and Delta S H 0 . These obtained parameters were in excellent agreement with the literature.