This study reports how the electrocatalytic activities of gold (Au) electrodes change with aging under ambient conditions. The enhanced electrocatalytic activities of Au electrodes observed after piranha treatment, mechanical polishing, or NaBH4 treatment decrease with aging. The enhanced electrocatalytic activities toward p-benzoquinone reduction and glucose oxidation decrease 7 days after the treatments, even though the change in surface contamination during aging is not significant. The surface roughness of the Au electrodes is maintained during the NaBH4 treatment, whereas it changes substantially during the piranha treatment and mechanical polishing. (C) 2012 Elsevier B.V. All rights reserved.