The permeability of H-2-selective palladium membranes fabricated with microsystem technology has been studied. The permeation experiments have been carried out at temperatures between 623 and 873 K at H-2 feed partial pressures of 0.2-1.0 bar. At 823 K, a permeance based on the free membrane area of 18 mot H-2/m(2) s bar 0.58 has been measured for a Pd membrane with a thickness of 0.5 mu m. From the permeation experiments the rate determining transport step and the stability of the membranes have been determined. At 873 K the H-2/He selectivity decreases rapidly, indicating the formation of pinholes at higher temperatures. From a combination of experiments and computer simulations the limiting transport step has been determined to be H-atom diffusion through the membrane at elevated temperatures and H-2 surface reactions at the retentate side at lower temperatures. (c) 2006 Elsevier B.V. All rights reserved.