Five N-alkylated derivatives of a poly(amidesulfonamide) polymerized from N,N＇-bis-4-aminophenylsulfonyl 1,3-diaminopropane and isophthaloyl chloride were synthesized. The new polymeric materials were used to prepare nonporous symmetric membranes. The membranes were characterized by IR spectroscopy, sorption measurements and wide-angle X-ray diffraction. During the pervaporation of 10% aqueous solutions of methanol, ethanol, propan-I-ol and propan-2-ol, membranes made from the parent and modified poly(amidesulfonamide)s were preferentially permeable to water and their separation factors were mainly dependent on the molecular weight of the permeant. By introducing an alkyl pending group to the backbone of the polymer, all modified membranes exhibited an enhancement in flux rate and a variation in separation factor in the pervaporation of aqueous alcohols. In the dehydration of ethanol, several modified membranes possessed separation characteristics that appeared to be superior to that of the parent membrane.