A novel water-soluble poly[N-(2-hydroxypropyl)methacrylamide] copolymers containing thiazolidine-2-thione reactive groups in the side chains suitable for preparation of polymer-modified biologically active compounds and water-soluble targeted polymeric anticancer drugs were synthesized and characterized. Copolymers containing thiazolidine-2-thione reactive groups were prepared by radical copolymerization in dimethyl sulfoxide. Molecular weight of the copolymers can be easily controlled by monomer and initiator concentrations and polymerization temperature. The copolymers containing thiazolidine-2-thione reactive groups showed low susceptibility to hydrolysis and high rate of aminolysis in aqueous solutions. The advantages of using TT copolymers for the synthesis of polymeric drugs are demonstrated on the synthesis of the polymer superoxide dismutase, polymer-doxorubicin and human immunoglobulin-targeted polymer-doxorubicin conjugates performed in aqueous solution in one-step procedure. (c) 2006 Elsevier B.V. All rights reserved.