Sorption and pervaporation experiments were carried outwith PVA/PAA cross-linked membranes for the separation of azeotropic methyl tert-butyl ether and methanol mixtures. The influence of the PVA/PAA ratio and liquid mixture composition were investigated. With increasing PAA content in the membranes, solubilities and fluxes decreased and selectivities increased. Total sorption and fluxes increased with increasing concentration of MeOH. Increasing the concentration of MeOH resulted in decreasing selectivities. Because of polarity, MeOH permeated selectively through the membranes. Sorption results showed the same tendency with pervaporation results.