Pervaporation properties of PESS ion-exchange membranes in contact with water-aliphatic alcohol mixtures were obtained. PESS ion-exchange membranes were prepared by chemical modification of the interpenetrating polymer network system polyethylene-poly(styrene-co-divinylbenzene). PESS membranes were loaded with different alkali metal ions as counterions. The obtained data showed that properties of PESS membranes depended strongly on the kind of counterions, degree of cross-linking, and difference in the polarities between water and organic component of the binary mixture. Results obtained for PESS membranes were compared with data obtained for Nation 117 ion-exchange membrane.