Separation of acetic acid-water mixtures by using evapomeation (EV) method were carried out over the full range of compositions at temperatures varying from 30 to 55 degrees C using poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) (75/25) (v/v) alloy membranes. PVA/PAA membranes gave separation factors of 110-5711 and permeation rates of 2.3x10(-4) -1.53x10(-1) kg/m(2)h, depending on the operation temperature and feed mixture composition. The temperature dependence of the permeation in EV was expressed by the Arrhenius type expression and the activation energy was calculated as 9.15 kcal/mol. More efficient EV technique, which is called temperature difference evapomeation method (TDEV) was also applied to PVA/PAA membranes to separate acetic acid-water mixtures; high permeation rates (1.7x10(-3) -3.0x10(-1) kg/m(2)h) and separation factors (1335-8924) were obtained for each of the studied feed compositions. Azeotropic mixture of acetic acid and water was also separated by TDEV method with a separation factor of 297 and permeation rate of 1.50x10(-1) kg/m(2)h.