The pervaporation separation of acetic acid-water mixtures was carried out over the full range of compositions at temperatures varying from 30degrees to 55degreesC using poly(vinyl alcohol) (PVA) membranes modified with poly(acrylic acid) (PAA). The best condition for the preparation of the membranes was found as PVA/PAA ratio as 75/25 (v/v). Effects of membrane thickness, operation temperature, feed composition on the permeation flux, and separation factor were investigated. PVA/PAA membranes gave separation factors of 34 to 3548 permeation rates of 0.03 to 0.60 kg/m(2) h, depending on the operation temperature and feed mixture composition. The temperature dependence of permeation rate for binary mixtures was expressed by the Arrhenius type relation and activation energy of 17.62 kcal/mol was calculated for the permeation.