In this paper a dynamic microkinetic model of the methanol synthesis reaction over Cu/ZnO catalysts is described. The model is based on surface science measurements and it includes the dynamic changes in particle shape and active surface area which have recently been observed by in situ EXAFS measurements to take place upon change in the redox potential of the reaction gas. It is suggested that the change in particle morphology is related to a change in the number of oxygen vacancies at the Zn-O-Cu interface. Furthermore, the structure sensitivity of the methanol synthesis reaction is also taken into account. The dynamic microkinetic model is seen to give a much better description of the kinetic measurements over a working methanol catalyst compared to a static microkinetic model. The new model also gives an explanation of the kinetic behavior during transient conditions. The dynamic aspects are seen to provide a basis for understanding the apparently conflicting reaction orders reported in the literature.