Cation exchange membranes polyethylene sulfonated polystyrene (PESS) were prepared by sulfonation of an interpolymer polyethylene/poly (styrene-co-divinylbenzene) [PE/poly(St-co-DVB)] with 1 or 3 wt% of the cross-linking agent divinylbenzene (DVB). Swelling properties of the PESS ion-exchange membranes in contact with water-aliphatic alcohols mixtures were investigated. The 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, the degree of cross-linking, and the difference in the polarities between water and the organic component of the binary mixture. Results obtained for PESS membranes were compared with data obtained for the Nation 117 ion-exchange membrane.