The paper deals with one of the most promising membrane separation processes - pervaporation. So far, only polymeric membranes have been used for industrial applications. After improving the preparation of separation layers, inorganic membranes could be an important competitor. The transport mechanisms in both types of membranes are described. The separations of a methanol - tert-butyl methyl ether mixture by pervaporation on polymeric and inorganic membranes are compared.