The electrochemical oxidation of NADH at glassy carbon electrodes modified with electropolymerized films of metal phthalocyanines was investigated. Three different polymers were used in this study, each incorporating a different central metal ion (M = Co, Ni, Zn). All were effective electrocatalysts for NADH oxidation, decreasing the overpotential by several hundred millivolts compared with the unmodified carbon surface. Peak potentials vary only slightly among the three types of modifying layers (for similar film thicknesses), suggesting that the nature of the central metal is a relatively unimportant factor in the catalytic process. The observed peak potentials decrease with increasing pH of the medium and also show a weak dependence on film thickness, scan rate, and electrolyte concentration. Anodic peak currents at the coated electrodes vary linearly with NADH concentration in the range from 20 muM to 3.0 mM. Although the peak currents decrease somewhat following the first few voltammetric scans, the response soon stabilizes, and a steady, reproducible NADH oxidation current is still observed after more than 100 cycles.