Dense poly (vinyl alcohol) (PVA) membranes of different crystallinities were prepared and studied in pervaporation of water-ethanol mixtures. High selectivities to water were obtained with all types of membranes. Permeation fluxes increase exponentially with the water content in the liquid mixture. At a given water content, the membrane permeability decreases drastically when its crystallinity increases. When the pervaporation temperature increases, the permeation flux increases according to the Arrheniuslike law, with a permeation acti-vation energy that depends strongly on the crystallinity of the membrane. A permeation model, in which the volume fraction of amorphous polymer intervenes in both the sorption and the diffusion laws, was proposed and validated by the experimental data. With the obtained values of the parameters, the permeation Olux can be calculated for membranes of a given crystallinity at any temperature and composition of the water-alcohol mixture. © 1993 John Wiley & Sons, Inc.