The selective oxidation of ethylene to ethyleneoxide and of methanol to formaldehyde both use a silver based catalyst and both are important industrial reactions. For both reactions, carbondioxide is an undesired byproduct, selectivity is a major issue for the catalyst and the reaction mechanism has been controversial. We have succesfully formulated microkinetic models for both reactions. The models are based on a plausible reaction mechanism and available measurements for the properties of reactant, intermediates and products. The models reproduce a large number of experiments including the reaction rate measured at industrial conditions and offer a framework for understanding the mechanism, kinetics and a wide range of experiments. The analysis of the models have been completed and are under publication. Researchers: Per Stoltze, Aalborg University, Esbjerg,                       Carsten Stegelmann, Aalborg University, Esbjerg,                       Hasse Lynggaard, Aalborg University, Esbjerg, Anders Andreasen, Materials Research Department, Risø,                       Niels Christian Schiødt, Haldor Topsøe A/S.