The effect of an alternating voltage signal on dissolution of platinum in aqueous 1.0 mol dm-3 HCl was investigated. Experiments were carried out in a three-electrode quartz cell using platinum (working electrode), saturated calomel electrode (reference) and graphite (auxiliary electrode). On platinum electrode was superposed an alternating voltage (AV) of 0.5 Vms and a direct voltage (DV) of 0.5 V (vs. ESC). AV frequencies were changed from 10 to 100 Hz. It was found platinum dissolution rate is increased by alternating voltage to an extent depending on the frequency. At constant frequency, it was observed sigmoid form for concentration-time curves of dissolved platinum. With sinusoidal AV of 100 Hz, the dissolution rate of platinum was 10-2 mg cm-2 s-1 in the linear region of the concentration- time curve. This effect was explained postulating that during the anodic half-cycle of the alternating signal, and after 0.5 V, the platinum dissolution and the oxide formation are competitive reactions, and platinum is dissolved at oxide free site on platinum electrode surface. During cathodic half-cycle, the platinum oxide is reduced and passivity is destroyed leaving the platinum susceptible to be attacked by chloride ions.