Glucose oxidase was entrapped between poly(2-hydroxyethyl methacrylate) membranes and conditions were optimized for high enzyme activity and high levels of entrapment. Highest entrapment was with a 78 mum thick coat. A continuous flow membrane reactor was designed and used. The reaction was first order with respect to glucose and to oxygen. V(max) values for the native and immobilized enzymes were 0.182 and 0.133 mm/min. The K(m)'s for native and immobilized enzymes were 6.2 and 16.9 mm, respectively. At high substrate concentrations enzyme poisoning was detected. Both pH and temperature profiles moved to higher values upon immobilization. The enzyme retained 80% of its activity for at least 3 months in dry form.