A chitosan/polysulfone composite membrane was prepared. The preparation procedure involved dissolution of chitosan in dilute aqueous acetic acid to form chitosan salt, coating of the chitosan salt solution on a porous polysulfone substrate, and regeneration of chitosan by alkaline treatment. The membrane was tested for selective removal of water from aqueous ethylene glycol solutions by pervaporation. The effects of operating parameters, including feed concentration, temperature, and downstream pressure, on the separation performance of the membrane were investigated. At 35 degrees C and 60 Pa downstream pressure, a permeation flux of 0.3 kg/m(2) h and permeate water concentration higher than 92 wt% was achieved at a feed water content of 10 wt%. This study demonstrated the potential of membrane pervaporation as an alternative to conventional distillation for the given separation. It was also shown that conditioning of the membrane in the pervaporation system at the maximum operating temperature led to a quasi-permanent change in membrane permselectivity.