A cross-linking polymeric layer containing molecular imprint sites of theophylline (THO) was formed on a polyacrylonitrile membrane, which had a photosensitive dithiocarbamate group, by photograft copolymerization. In the presence of THO template molecules, aqueous solutions of N,N＇-methylenebisacrylamide (MBAA) and acrylic acid (AA) were used for the photoinitiated polymerization. After the photograft polymerization, removal of the template was carried out and then an aqueous solution of THO or caffeine (CAF) was permeated through the resultant membrane. It was found that the polymeric layer of MBAA and AA formed on the membrane surface can recognize with high efficiency the THO molecule and take it up into the surface layer of the membrane. Relative to THO, CAF was not taken up effectively by the membrane. The results indicated that the photograft treatment is useful for the formation of the THO-imprinted polymeric layer on the membrane surface.