In this study, alpha-chymotrypsin was immobilized via physical entrapment within thermally reversible poly(isopropylacrylamide-co-hydroxyethylmethacrylate), poly(NIPAM-co-HEMA) copolymer gels. The thermoresponsive gel matrices in cylindrical geometry were prepared in an aqueous buffer medium by a redox polymerization method. The kinetic behavior of enzyme-gel cylinders was investigated in a batch reactor. The results indicated that the overall reaction rate was controlled by the substrate diffusion through the gel matrix. Due to the thermoresponsive character of the carrier gel, the maximum activity was achieved at 30 degrees C with the enzyme-gel system while the free enzyme exhibited maximum activity at 40 degrees C.