An enzyme support system is prepared by dropping a mixture of acrylic acid, methyl methacrylate, polyethylene glycol (mw, 1000) and enzyme into supercooled petroleum ether followed by γ-radiation. The particles obtained by this procedure are spherical (1.5 mm in diameter) in shape and are in the form of a white gel. After radiation, the spherical polymer granules are placed in a vessel and the noncrosslinked polyethylene glycol is dissolved in water in order to achieve a porous gel structure. To test the feasibility of using this system as an enzyme support, urease is immobilized by optimizing the radiation dose and ratio of components. Activity yield of enzyme is found to be 30-80% of the native enzyme. The highly porous structure of this system offers the advantage of enabling a large enzyme loading per gram polymer. Besides this, the gel form leads to the achievement of high rates of diffusion into the particles. It is thus reasonable to conclude that these hard, spherical gel particles might be a suitable support system for enzyme immobilization. © 1984 Humana Press Inc.