Glucose-sensitive hydrogels (GSHs) responsive to both pH value and glucose concentration have been prepared by polymerizing solutions containing hydroxypropyl methacrylate, (N,N-dimethylamino)ethyl methacrylate, and tetraethylene glycol dimethacrylate in the mole ratio 70:30:2. Various concentrations of both glucose oxidase (GOx) and catalase were physically immobilized in the hydrogel matrix. The presence of GOx makes the hydrogels glucose-responsive, and catalase was added in order to explore its effects on swelling kinetics. In response to pH changes, hydrogels containing varying amounts of catalase show identical swelling kinetics and identical equilibrium degrees of swelling. However, in response to increases in glucose concentration, the rate of GSH swelling is dramatically increased by the presence of catalase when GOx activity is limited by the amount of oxygen available. In addition, catalase improves the enzymatic stability of the GOx by converting hydrogen peroxide to water.