The main quantitative results from Wagner's oxidation theory are recalled while the conditions of application of that theory are reviewed from the point of view of oxidation kinetics like those of chromium, zinc, and iron. Bibliographical results on cobalt and copper oxidation and on cobaltous and cuprous oxides are quantitatively compared to Wagner's theory. In the same, the validity of the cation self-diffusion coefficient determination by the parabolic constant is considered. Finally, the modification of a rate equation to take a surface reaction into account is discussed.