Dual catalysts of varying glucose oxidase (EC 1.1.3.4) and catalase (EC 1.11.1.6) activities were constructed by immobilization of the enzymes to silanized nickel silica alumina with glutaraldehyde. The amount of product formed and the efficiency of the systems were determined using either of the enzymes to initiate the cyclic reaction. The former depends on the activity of both enzymes in the system while efficiency describes how well the second enzyme in the sequence utilizes the intermediate of the reaction. Efficiency was a function both of the ratio of the two activities and their absolute values. An increase in the activity of the second enzyme of the reaction sequence of a decrease in the activity of the first enzyme increased the efficiency. A higher efficiency was observed with higher absolute activities of the enzymes when the ratios of the enzyme increased the efficiency. A higher efficiency was observed with higher absolute activities of the enzymes when the ratio of the enzymes was constant. Dual catalysts were compared to mixed catalysts (each enzyme immobilized to separate particles) and to soluble, homogeneous systems at equal total activities. In general, the dual catalysts were superior to either of the others. Computer simulations of the reaction rates indicated that all experiments were performed in the lag period of the two-step reaction.