Electrochemical selective detection of not only As(III) but also As(V) has been investigated by anodic stripping voltammetry. Here, instead of using modified working electrodes, simple as-deposited boron-doped diamond (BDD) electrodes were used with the addition of gold ions in the sample solution as a catalyst for the electrochemical reaction. A potential-step technique was performed to minimize the hydrogen evolution effect that occurs at the highly negative potential Such as -1 5 V (vs. Ag/AgCl) for the reduction of As(V). The present method realized very high sensitivity with an experimental detection limit of 12 ppb and excellent stability for the detection of both As(III) and As(V) as well as mixed solutions of these forms.