A mordenite membrane was synthesized on a ceramic tubular support by seeded hydrothermal synthesis and tested in the dehydration of a water/ethanol mixture by pervaporation. The influence of synthesis conditions (time and gel composition) on the water/ethanol separation factor and water flux was investigated. Typical membranes yielded a water/ethanol separation factor of 150, at a water flux of 0.2 kg/m(2.)h. The XRD patterns showed that mordenite was the only zeolite material present in the membrane.