Using electrochemical impedance spectroscopy and a relaxation method with galvanostatic perturbation the kinetics and mechanism of the magnesium electrode reaction in six melts oi the binary MgCl2 - NaCl system were determined at several temperatures. A three-step electrode process was found. the high frequency one being pure charge-transfer whereas the low frequency one showing mixed charge transfer-diffusion character. The exchange current density for the high frequency step is in the range from 20 to 50 A cm(-2) whereas for the low frequency step it varies from 3 to 10 a cm(-2). On the basis of the corresponding exchange current densities and structural and thermodynamic data, a mechanism of the overall electrode reaction in these melts is proposed. The course of the low frequency exchange current density with the composition, corresponds to the change of the MgCl2 thermodynamic activity in the more dilute solutions of MgCl2 in the melt.