Carbon modified by the reduction of aromatic diazonium derivatives was first used as electrode for the electrochemical stripping analysis of heavy metals. As a model, the glassy carbon electrode was modified with benzoic acid by electrochemical reduction of diazobenzoic acid, and the resulting modified electrodes were used for determination of Cd 2+ and Pb 2+ . The anodic peak currents of cadmium and lead at the benzoic acid-modified glassy carbon electrode are 7.2 and 6 times of that at the bare glassy carbon electrode. A linear response was observed for Pb 2+ and Cd 2+ in the range of 0.5–50μg/l. The detection limits are 0.20μg/l for Pb 2+ and 0.13μg/l for Cd 2+ . The relative standard deviations for six consecutive measurements of 50μg/l Cd 2+ and 50μg/l Pb 2+ are 0.82% and 3.02%, respectively. Applicability of the sensor to the determination of Cd 2+ and Pb 2+ in sewerage samples was demonstrated.