The nitriding of magnesium in pure nitrogen shows two distinct types of kinetic behavior at temperatures in the range 385–650°C. Below 500°C, the reaction follows a normal linear law resulting from a metal-gas interfacial reaction determining the kinetic processes. Above this temperature, a vapor phase nitriding reaction is superimposed onto the interfacial reaction due to the simultaneous sublimation of metal from the surface. Both the nitriding and sublimation kinetics are markedly dependent on the nitrogen pressure in the range 50–760 mm Hg.