Glucose was continuously determined by reaction in a packed-bed enzyme reactor containing glucose oxidase and catalase. Oxygen consumption was measured amperometrically with a polarographic Clark electrode. Glucose was sampled through a dialysis probe immersed in the solution to be measured. An extension of the normal range for the enzyme was achieved by modulating the flow rate through the dialysis probe and a linear response was obtained in the range of 1.0-60 mM glucose. The correlation between the glucose transfer and the membrane area of the dialysis probe was also studied. Six different membranes were used, all showing variations in the adhesion of yeast cells.