The kinetics of the anodic reaction occurring during the electrolysis of molten nitrates on bright platinum electrodes has been studied. The kinetic parameters were obtained from conventional current/potential curves, build-up of electrode potential at constant current density and decay of anodic overpotential, working at temperatures between 220 and 470°C. The current density was varied between 1 and 500 mA/cm2. In the region 220–290°C the Tafel slope approaches 2RT/F as given by the current/potential curves, but for decay curves, when overpotential is plotted against log t, two straight line portions, one with slope 2RT/F and the other with slope RT/F were observed. The transition from one straight line to the other occurs abruptly. The exchange current densities for both portions were calculated. These results are explained considering a consecutive scheme of reaction where at least two steps differently dependent on electrode potential can be rate-controlling in the mechanism of reaction. In the range between 350°C and above, the Tafel slope is clearly RT/F, independent of the method of measurement. The exchange current density was also determined and the mechanism of the reaction interpreted in terms of the increase of oxide-ion concentration with temperature and the discharge of these ions on platinum electrodes.