Studies of evolution kinetics on iridium anodes on which oxide films of various thicknesses from a monolayer upwards were formed by a potential cycling program, are reported. The multilayer oxide films were of the kind that exhibit reversible reduction/oxidation behavior. The kinetic experiments conducted in aq. at pH 2 give log [current] vs. overpotential relations having a constant Tafel slope of for all anode oxide surfaces prepared, indicating that the evolution mechanism is independent of the thickness of the oxide film produced. However, the apparent exchange current densities increase in an almost linear way with thickness. The latter behavior is attributed to an increase in the real area of the electrode available for Cl−discharge, coupled possibly with improved electrocatalysis, e.g., on account of changes that can arise in the band structure of the oxide. Increases of evolution rates of up to ca. 180× are found. Effects of Cl− adsorption on the development of the initial monolayer of oxide of Ir were also studied and compared with the behavior at Pt. Cl− adsorption is found to inhibit the formation of the thick oxide films at Ir.