The pervaporation separation of aqueous ethanol mixtures was carried out using a series of polyimide membranes. The soluble polyimides were prepared from 3,3',4,4'benzhydrol tetraacarboxylic dianhydride, BHTDA, with various diamines. The aromatic diamine structure effects on the membrane properties were investigated. The feed compositions, degree of swelling and feed solution temperature effects on the pervaporation performances of aromatic polyimide membranes were studied.