Results of kinetic investigations on the basis of isothermal DSC measurements by means of defined pressure changes are presented and interpreted for the Mg/MgH2 system. From an evaluation of the experimentally obtained DSC-signals, the dependence of reaction rate on hydrogen pressure p(0), temperature and sample morphology could be described. Under certain conditions, it is possible to visualise individual rate-determining steps and, thus, to arrive at conclusions on the reaction mechanism.