This paper deals with a systematic study of mercury deposition from sodium chloride solutions to determine the feasibility of using this reaction for mass-transfer measurements. The study was performed with a glassy carbon rotating disc electrode and reproducible results were obtained only when the electrode was catodically pretreated. Polarization curves at different concentrations of sodium chloride and mercury (II) are reported. Hydrogen evolution and oxygen reduction has also been considered as side reactions and the conditions where their influence may be neglected are discussed. Experimental conditions where mercury deposition can be used as test reaction are given.