Two novel A-B-A type amphiphilic triblock copolymers, namely poly(N-(2-hydroxypropyl)methacrylamide)-block-poly(epsilon-caprolactone)-block-poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA-b-PCL-b-PHPMA) and poly(N-vinyl-2-pyrrolidone)-block-poly(epsilon-caprolactone)-block-poly(N-vinyl-2-pyrrolidone) (PVP-b-PCL-b-PVP), were synthesized and characterized. These polymers were prepared by free radical polymerization of N-(2-hydroxypropyl)methacrylamide and N-vinyl-2-pyrrolidone in the presence of a novel biodegradable, macromolecular chain-transferring agent, alpha,omega-poly(epsilon-caprolactone) dithiol (HS-PCL-SH). All triblock copolymers self-assembled in aqueous solutions to form supramolecular aggregates of 30-200 nm size. The critical aggregation concentration of the polymers ranged from 1 to 4 mg/L. The partition equilibrium constant (K-v) of pyrene in the hydrophobic core of micelles was comprised between 2.5 x 10(5) and 4.2 x 10(5). The triblock copolymer micelles were loaded by a dialysis procedure with 1-4% (w/w) of two model poorly water-soluble drugs, i.e., doxorubicin and amphotericin B. These triblock copolymers could prove useful as nanocarriers for the solubilization and transport of hydrophobic drugs. The bifunctional macromolecular chain-transferring agent reported in this work can also find application in the synthesis of a variety of novel A-B-A type biodegradable triblock copolymers.