The anodic dissolution of gold, coupled with anodic oxide formation, in aq. HClO4 in the presence of various concentrations of Br- ions was studied using cyclic voltammetry and chronoamperometry, complemented by nanogravimetry using an electrochemical quartz crystal nanobalance (EQCN). The results clearly indicate that gold initially dissolves through a 3e(-) oxidation process, qualitatively supported by UV-vis spectrometry. The kinetics of the Au dissolution process was evaluated using CV, EQCN, chronoamperometry, and rotating-electrode experiments. The linear relationship between mass change and inverse of square root of sweep-rate and between-anodic peak currents at ca. 1.16 V (RHE), and square root of sweep-rate indicated quantitatively that the dissolution process is diffusion-controlled. (C) 2003 Elsevier Science B.V. All rights reserved.