The preparation and properties of solid-supported urease (urea amidohydrolase, EC 3.5.1.5) are described. The supported enzyme derivatives were made by adsorbing the enzyme onto the surface of kaolinite. The preparations made at various pH values between 4.3 and 9.0 were found to have the enzyme protein attached irreversibly. The supported enzyme showed a considerable activation at all pH values except at pH 4.3, the maximum increase in activity being nearly twofold. The pH optimum for the enzyme remained unchanged at pH 6.65 with Km values showing an increase at most pH values.