Hydrogen permselectivity and poisoning resistance of nanostructured palladium-iron alloy films were examined to evaluate these materials for potential membrane applications. At 200 degreesC, nanostructured palladium-iron films had hydrogen/helium selectivities of up to 35:1 and hydrogen fluxes of up to 10 sccm/cm(2). The rate-limiting step for hydrogen transport was diffusion through the bulk metal. Hydrogen flux in the nanostructured palladium-based membranes decreased with increasing iron content. The nanocrystalline membranes had higher hydrogen fluxes than coarse-grained polycrystalline systems of similar compositions. Nanostructured membranes also exhibited better resistance to hydrogen sulfide poisoning than polycrystalline membranes. When applied for the hydrogenation of ethene, the palladium-iron nanocrystalline membranes displayed stable activities over long time periods.