The structure and chemistry of support materials play an important role in zeolite film formation and have a significant influence on the separation property of the membrane material. Surface roughness and pore size define the optimum zeolite crystal size and membrane thickness. The chemical nature of the support surface influences zeolite nucleation, crystal growth and film adhesion. It has been demonstrated that chemical modification of the support surface can significantly alter the zeolite film formation. Ultrathin layers (20 nm) of metal and metal oxides have been deposited onto porous stainless steel support. This method gives highly reproducible film microstructure and has a good potential for large-scale application for zeolite membrane production. The effects of surface functional groups (-SiO2, -OH and -COOH) were simulated using adsorbed surfactants. In addition, the influence of ageing and seeding on zeolite film formation have also been investigated. (C) 2000 Elsevier Science B.V. All rights reserved.