A glutamate biosensor was developed by electropolymerizing o-phenylenediamine on a dehydrogenase-NAD+ modified carbon paste electrode. The amperometric response to glutamate was obtained by means of the electrocatalytic oxidation of the enzymatically produced NADH, at an applied potential close to 0 V (Ag/AgCl). After optimizing carbon paste composition, polymer thickness and operating variables, a linear amperometric response to glutamate was obtained within the concentration range 5.0 x 10(-6)-7.8 x 10(-5) M with a detection limit of 3.8 x 10(-6) M. The biosensor was applied to the determination of glutamate in chicken bouillon cubes. Good accuracy was found with respect to a reference enzymatic spectrophotometric method.