A simple electroless palladium plating treatment on V and V-15Ni alloy was attempted to prepare sandwich-type membranes for hydrogen purification. The obtained coating on the membranes was characterized using SEM-EDX and AFM, and hydrogen permeability and hydrogen diffusion coefficients for the plated membranes were determined. Sensitizing-activating treatment with SnCl2 and PdCl2 solutions before the electroless plating treatment enabled palladium to cover the membranes densely. The V membrane with electroless palladium plating, whose hydrogen permeability was 5.0 x 10(-7) mol H-2 m(-1) s(-1) Pa-1/2 at 623 K, showed cracking during the hydrogen permeation experiment at 473 K. Hydrogen permeability for the V-15Ni membrane with electroless palladium plating was 3.4 x 10(-8) mol H-2 m(-1) s(-1) Pa-1/2 at 623 K, which was comparable to that of the sample coated by the conventional methods including evaporation and electrochemical plating. The long-period permeation test showed that the V-15Ni membrane with electroless palladium plating possessed satisfactory durability to be used as hydrogen purification material. (C) 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.