A sensitive method is described for the determination of cefaclor by cathodic stripping voltammetry at the hanging mercury drop electrode. cefaclor is accumulated at the electrode surface as a mercury salt, which is reduced at −0.67 V. The optimum accumulation potential and accumulation time were +0.15 V and up to 180 s, respectively. Linear calibration graphs were obtained between 3.9 μg.L−1to 39 μg.L−1and the limit of determination was evaluated to be 1.9 μg.L−1. The method was applied successfully to the determination of cefaclor in pharmaceutical formulations.