The pervaporation separation of water-isopropanol mixtures was carried out using carboxymethylated poly(vinyl alcohol) (CMPVA) composite membranes. Carboxymethylated PVA (CMPVA) was synthesized by reacting PVA with various concentrations of monochloroacetic acid. Substitution efficiency of the CMPVA ranged from 12-32%. The cross-sectional structure of the composite membrane for pervaporation was confirmed by scanning electron microscopy (SEM) exhibiting a 20-mu m active skin layer. Glass transition temperature of the CMPVA was in the range of 74-84 degrees C, and decreased with increasing substitution efficiency. Degree of swelling and permeation flux for water-isopropanol in pervaporation increased with the substitution degree of carboxymethylation. CMPVA composite membrane, having 16% substitution efficiency, showed the following pervaporation performance; permeation flux of 831 g/m(2) h and separation factor of 362 measured at 80 degrees C and 85 wt % feed isopropanol concentration.