The pervaporation separation of water/ethanol mixtures through poly(sulfone-amide) membranes was investigated. Several poly(sulfone-amide) membranes were prepared by condensation copolymerization of bis(3-aminophenyl) sulfone, m-phenylenediamine, and isophthaloyl dichloride. The effects of the polymer composition were investigated for flat dense membranes. The copolymer membranes that contained 30 mol% m-phenylenediamine showed the maximum separation factor (= 2400). The asymmetric hollow fiber membranes were prepared by dry-jet-wet spinning method for the DMAC solution of this copolymer. In order to obtain a high separation factor, it was necessary to carry out heat treatment at near T(g). After heat treatment, these membranes had the separation in the 300 approximately 400 range and the permeation rate of 10 approximately 20 g/m2.h for ethanol/water mixture of 95 : 5 wt at 60-degrees-C. These membranes had their internal skin layer faced to the permeate side of pervaporation. The thickness of skin layer was found to affect the pervaporation properties. Further, the effects of the feed concentration and elapsed time were investigated. The pervaporation properties were dependent on swelling behavior.