Double-layer effects for the reduction of Co(NH3)63+ and Fe(H3O)63+ have been examined at a freshly annealed Au (100) electrode in aqueous HClO4 solutions. Marked changes in the reduction current are observed after the electrode is cycled through a positive potential at which surface reconstruction is lifted. The observed effects are attributed to the large shift in the potential of zero charge which accompanies reconstruction, and to changes in electrode area.