Copolymers bearing 5.6, 9, or 11.7 mol % of adenine residues were prepared by radical copolymerization of 2-ethylacrylic acid (EAA) and 9-[[2-(methacryloyloxy)ethoxy]methyl]adenine (MAAd). A double-chain surfactant with thymine in the headgroup was synthesized and used in mixtures with egg yolk phosphatidylcholine (EYPC) to prepare thymine-labeled unilamellar lipid vesicles. Analysis of the pH-dependent behavior of the copolymers revealed that release of contents could be effected from labeled vesicles in competitive experiments in which unlabeled vesicles remained intact. Selectivity was greatest for the 9 mol % copolymer and was reduced at either lower or higher levels of adenine labeling. The selective recognition of the labeled membranes is ascribed to interactions between polymer-bound adenine and surface-bound thymine functional groups.