Glucose dehydrogenase, a coenzyme-dependent oxidoreductase, was immobilized by a polyacrylamide gel matrix over the surface of a platinum screen to measure the glucose concentration in 0.1 M phosphate buffer, pH 7.4 at 25 and 37°C. The oxidation of β-D(+)-glucose in this enzyme reaction produced a zero-current potentiometric response over a limited range of glucose concentrations. The presence or absence of an electron mediator, ferricyanide, appears to have no observable effect on the electrode response. Concurrent spectrophotometric detection of NADH confirms that the zero-current potential produced was the result of the enzymatic coupled reactions. The temperature effects and the reusability of this immobilized GDH electrode in the mode of potentiometric measurement were investigated and described.