The separation performances of an aqueous ethanol solution through chitosan dip-coated chitosan/polysulfone (PSf) composite hollow-fiber membranes with the vapor permeation operating process were investigated. The effects of chitosan concentration and dip-coated temperature on the separation performances were studied. Compared with unmodified PSf hollow-fiber membranes, chitosan dip-coated polysulfone (PSf) composite hollow-fiber membranes can effectively increase the permselectivity of water. By increasing the concentration of chitosan solution, the permeation rate as well as ethanol content in permeate decrease. In addition, the effect on the vapor permeation performances of the feed composition and feed solution temperature were also investigated. The permeation rate decreases while the separation factor toward water increases with increasing ethanol concentration in the feed. Moreover, the permeation rate increases while the separation factor toward water decreases with increasing feed temperature. The permeation rate, separation factor and Psi at 25 degrees C for a 90 wt% aqueous ethanol solution through the chitosan/PSf composite hollow-fiber membrane with a 3 wt% chitosan dip-coated system were 63 g/m(2) h, 2440, and 153,700, respectively.