Transient as well as steady-state kinetic experiments were applied for the derivation of the reaction mechanism and kinetic constants of the water-gas shift reaction over a Pt/MgO catalyst. Separate investigations on Pt-black and MgO were performed to elucidate the interaction of the metal and support component in the catalytic process. The rate of equilibration of the water-gas shift reaction was compared with the rates of methane conversion to syngas by steam reforming, CO2 reforming and partial oxidation. Among these reactions the water-gas shift reaction is the fastest reaction step. CO2 and H2 adsorbed on MgO, OH-groups on MgO as well as CO adsorbed on Pt should be the reactive surface species. Hence, Pt as well as MgO play an important role in the catalytic process. While MgO provides sites for CO2 adsorption and H-2 activation, the formation of stable Pt-CO adsorbates should be the driving force of CO2 dissociation.