Pd and Pd-Ag alloy porous thin film membranes on a ceramic alpha-A1(2)O(3) tubular membrane support have been characterized by SEM, XRD and TPR measurements and reactivity studies in the direct H2O2 synthesis from H-2/O-2. The brittleness of the Pd film due to formation of palladiumhydride in the presence of H-2 diffusing through the membrane is a major problem, which causes a fast deactivation of the membrane with formation of pinholes and finally rupture of the thin film. The formation of an alloy with Ag prevents this problem, but decreases the catalytic performances in the synthesis of H2O2. By preparing multilayer catalytic membranes with a Pd-Ag interlayer between the ceramic support and the final Pd thin film it is possible to couple high catalytic performances and good stability of the membrane. (c) 2006 Elsevier B.V. All rights reserved.