Membranes of poly(acrylonitrile-co-acrylic acid) made by phase inversion technique in the presence of tetracycline hydrochloride showed molecular recognition behavior towards the template molecule. The interactions of the carboxylic groups of the polymer chain played an important role in the discrimination process. Prolonged washing with distilled water regenerated the membrane without any loss of binding capacity. Chloramphenicol, of similar polarity and fair solubility in water, is recognized less efficiently. © 2004 Elsevier B.V. All rights reserved.