A new polymeric drug carrier system using amino acid-based polymers was developed. Amino acid-based polymers with controlled molar mass and narrow molecular weight distribution have been synthesized by reversible addition-fragmentation chain transfer polymerization of four amino acid-carrying monomers having different chirality and hydrophilicity. Metronidazole (MTZ) was immobilized onto the amino acid-based polymers, and the release profiles of the polymer-MTZ adducts were investigated in phosphate buffer solutions (pH = 2.0, 7.4, and 8.5). The model drug was released by the hydrolysis of the ester group, and the release rate and behavior of the polymeric prodrugs strongly depended on the configuration of the amino acid-based polymers-MTZ adducts and the pH of the release media. The release kinetics was determined using the Higuchi and Korsmeyer equations, which revealed the release mechanism of the polymeric prodrugs. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013