The ZSM-5 type membrane was prepared on a flat cordierite Support by low temperature chemical vapor deposition (LTCVD) of a silica layer, followed by an in situ crystallization in vapor phase. The membrane obtained consisted of loosely -packed zeolite crystals in the pores of the support, The silica-alumina ratio of the membrane zeolite layer determined by EM was low, indicating it hydrophilic nature of the membrane. The performances of the ZSM-5 membrane in the separation of water-alcohol mixtures by pervaporation were Studied and discussed with respect to the membrane structure and the alcohol nature. The membrane showed very high selectivity towards water in the water-ethanol mixture. The transport mechanism of the membrane has also been discussed. (C) 2005 Elsevier B.V. All rights reserved.