A sol-gel method was applied for the preparation of palladium-doped silica membranes for hydrogen separation. Hydrogen permeation performance and stability (thermal, hydrothermal) were evaluated by measuring the time and temperature dependence of gas permeances (N(2), H(2) , He) in N(2) and steam atmospheres (steam: 70 kPa) at 500 degrees C, respectively. It was found that the Pd-doped silica layer has a thickness of approximately 80 nm, and Pd particles of several nanometers were well dispersed in an amorphous silica matrix. Pd-doped silica membranes (Si/Pd=3/1) fired at 550 degrees C in air were quite stable in N(2) atmosphere at 500 degrees C, but a drastic decrease of gas permeances (He, H(2), N(2)) and an increase of activation energy of gas permeation (He, H(2)) were observed under H(2) atmosphere at 500 degrees C due to aggregation of Pd particles. Pd-doped silica membranes (Si/Pd=3/1) fired at 550 degrees C in H(2) showed high stability in hydrogen and steam atmospheres (steam: 70 kPa) at 500 degrees C. This is because well-dispersed Pd particles in amorphous silica networks could not move in hydrogen and steam atmospheres.