Palladium (Pd) impregnated alumina membrane is prepared by sol-gel technique for hydrogen separation. Direct impregnation of Pd is achieved by mixing the alumina sol with a Pd precursor, followed by sonication to disperse Pd particles uniformly throughout the membrane. Hydrogen selective gamma-alumina membrane containing Pd particles is formed as an intermediate layer in an asymmetric porous support. The average pore radius and surface area measured by BET are 20.8 Angstrom and 217.4 m(2)/g, respectively. The dispersion of Pd in the membrane is 0.31 and the particle size is 32 Angstrom, both determined from Hz chemisorption experiment. Permeation fluxes through the membrane are also measured for various gases. The results show that impregnation of small amount of Pd can enhance the selectivities of hydrogen relative to both nitrogen and carbon dioxide up to 9.86 and 8.11, respectively, due to the surface diffusion of adsorbed hydrogen. The separation efficiency for hydrogen becomes much better at the lower bulk pressure. However, the hydrogen selectivity is not a monotonic function of temperature and there exists an optimum temperature which is dependent upon the adsorption kinetics of gas molecules.