The theophylline imprinted membrane was prepared by a wet phase inversion method. Theophylline was implanted during copolymerization of acrylonitrile with acrylic acid or implanted in the dimethyl sulfoxide solution containing10 wt% copolymer, p(AN-co-AA). Rolling the glass plate, on which the copolymer solution was cast, in water removed the sponge layer and thus made the membrane symmetric. The adsorption selectivity of the membrane toward template molecule was increased with the coagulation temperature of the membrane and the initial concentration of the theophylline and caffeine mixture.