The kinetics of the oxidative dehydrogenation of butane on a V/MgO catalyst has been studied under anaerobic conditions. In these conditions the oxygen from the catalyst lattice is consumed by the reaction, and the oxidation degree of the catalyst changes during the experiment. A kinetic model is proposed in which each reaction rate is related with the oxidation degree of the catalyst. The whole kinetic model is useful for the modelling of reactors where the catalyst operates in non-steady state, i.e. where the oxidation degree of the catalyst changes with time. It has also been found that whereas the main contribution to the oxidative dehydrogenation reaction comes from the lattice oxygen, there is also a non-selective contribution from weakly adsorbed oxygen. (C) 2003 Elsevier Ltd. All rights reserved.