Both the adsorption of Au-containing species on a polycrystalline gold electrode in alkaline 10(-4) M dicyanoaurate solution and the heterogeneous isotope exchange of Au atoms in this system were studied by the use of ＇electrode lowering＇ radiotracer techniques and Au-195-labelled dicyanoaurate. At an electrode potential of 0.1 V (SHE), the rate of adsorption of Au-containing species is considerably higher than that of heterogeneous isotope exchange which makes it possible to discriminate the contribution of adsorption from that of heterogeneous isotope exchange. The surface concentration of Au-containing species adsorbed on the gold electrode at 0.1 V determined in this study is close to that of CN-containing species adsorbed in the same system obtained previously [1]. The results obtained suggest strongly that AuCN species are adsorbed on a gold electrode from alkaline dicyanoaurate solutions and the heterogeneous isotope exchange is confined to the atomic monolayer of gold. The rate of heterogeneous isotope exchange at 0.1 V is some orders of magnitude higher than the partial cathodic current density extrapolated to this potential.