A lipoprotein lipase (LPL) was made water insoluble by immobilizing onto the surface of polyacrolein (PAA) microspheres with and without oligoglycines a s spacer. The activity of the immobilized LPL was found to remain high toward a small ester substrate, p-nitrophenyl laurate (pNPL). The relative activity of the immobilized LPL without spacer decreased gradually with the decreasing surface concentration of the immobilized LPL on the PAA microsphere. On the contrary, the immobilized LPL with oligoglycine spacers gave an almost constant activity for the substrate hydrolysis within the surface concentration region studied and gave a much higher relative activity than that without any spacer. The Michaelis constant K,,, and the maximum reaction velocity V,,, were estimated for the free and the immobilized LPL. The apparent K,,, was larger for the immobilized LPL than for the free one, while V,,, was smaller for the immobilized LPL. The pH, thermal, and storage stabilities of the immobilized LPL were higher than those of the free one. The initial enzymatic activity of the immobilized LPL maintained almost unchanged without any leakage and inactivation of LPL when the batch enzyme reaction was performed repeatedly, indicating the excellent durability of the immobilized LPL.