BACKGROUND: Solute rejection by a molecularly imprinted membrane was observed for the first time. Enantioselective poly[ (acrylonitrile)-co-(acrylic acid)] membranes were prepared by a wet-phase inversion method using D-phenylalanine (D-Phe) and L-phenylalanine (L-Phe) as templates, separately, in order to compare the imprinting effects of these isomers using an ultrafiltration experiment. RESULTS: Recognition sites were successfully created in the prepared membranes, which had a nanoporous structure. The rejection selectivities of 0.13 and 0.28, adsorption selectivities of 2.25 and 2.40 and permselectivities of 1.94 and 2.08 were achieved for the D-and L-Phe-imprinted membranes, respectively, after 16 mL (34 min) of ultrafiltration. CONCLUSION: Solute rejection by a molecularly imprinted membrane was selective. The performance characteristics ofboth the D- and L-Phe-imprinted membranes were different. Thus, the selection of an appropriate stereoisomer as a template plays an important role in the imprinting of membranes with regard to chiral resolution by ultrafiltration. (c) 2008 Society of Chemical Industry.