We have investigated the pervaporation separation of ethanol/water mixtures utilizing composite membranes prepared by coating a thin film of a polystyrenesulfonate across the surface of a microporous alumina support membrane. Such composite membranes are designated PSS/Al2O3 composites in this paper. The results show that PSS/Al2O3 composite membranes can break up the azeotrope of the ethanol/water mixture by pervaporation. Water is the preferred permeate for all membranes and all feed compositions. Membranes in the Na+ counter-ion form (PSS Na) showed higher separation factors than membranes having Mg2+ as the counter-ion (PSS-Mg). The separation factors for the membranes of 10.5 mol% sulfonate are one order of magnitude greater than the membranes of 27.5 mol% sulfonate. The membranes of 10.5 mol% of sulfonate, however, show overall permeate fluxes that are one order of magnitude lower than the membranes of 27.5 mol% sulfonate. The highest separation factor (400) was observed for the 10.5 mol% PSS-Na/Al2O3 composite membrane at the azeotropic feed composition. Ethanol weight fraction in the permeate is always less than 6 wt% for this composite membrane and all feed compositions.