Mercury deposition onto microcrystalline graphite and glassy carbon electrodes from aqueous chloride media was studied by Electrochemical Quartz Crystal Microgravimetry (EQCM) and voltammetric techniques. After deposition of Hg(0) under controlled potential conditions, mercury continued to deposit at open as a calomel film by the reaction, Hg + Hg(II) + 2Cl(-) <----> Hg(2)Cl2((aq)). The implications for the preparation of mercury film electrodes and for anodic stripping voltammetry are discussed.