The grafting of a poly(ethylene glycol) diacrylate macromer onto a chitosan backbone was carried out with different macromer concentrations. The grafting was achieved by (NH4)(2)Ce(NO3)(6)-induced free-radical polymerization. Biodegradable, pH- and thermally responsive hydrogels of poly(ethylene glycol)-g-chitosan crosslinked with a lower amount of glutaraldehyde were prepared for controlled drug release studies. Both the graft copolymers and the hydrogels were characterized with Fourier transform infrared, elemental analysis, and scanning electron microscopy. The obtained hydrogels were subjected to equilibrium swelling studies at different temperatures (25, 37, and 45,C) in buffer solutions of pHs 2.1 and 7.4 (similar to those of gastric and intestinal fluids, respectively). 5-Fluorouracil was entrapped in these hydrogels, and equilibrium swelling studies were carried out for the drug-entrapped gels at pHs 2.1 and 7.4 and 37 degrees C. The in vitro release profile of the drug was established at 37 degrees C and pHs 2.1 and 7.4. (c) 2006 Wiley Periodicals, Inc.