A polymeric microsphere (PM) with an epoxy group was prepared by the radiation-induced polymerization of glycidyl methacrylate and diethylene glycol dimethacrylate in reaction conditions with variations in solvents, irradiation dose, and monomer composition. The epoxy group of the PM was analyzed by solid-state C-13-NMR, Fourier transform infrared spectroscopy (FTIR), Fourier transform Raman spectroscopy, and elemental analysis (EA) after amination. In EA after amination, the epoxy group content was in the range 0.20-0.50 mmol/g. The lipase was immobilized to the epoxy group of the PM in experimental conditions with variations in the pH and the epoxy group content. The activity of the lipase-immobilized PM was in the range 148-342 unit/mg min. The activity of lipase-immobilized PM increased in accordance with the epoxy group content. The lipase-immobilized PM was also characterized by FTIR and EA. (C) 2003 Wiley Periodicals, Inc.