The effect of the pre-treatment temperature and atmosphere on the surface composition and on the activity and stability of well defined Au/CeO2 catalysts in the low-temperature water-gas shift reaction in dilute water gas was investigated by X-ray photoelectron spectroscopy, kinetic measurements and in-situ IR spectroscopic (DRIFTS) measurements, comparing different reductive and oxidative conditioning procedures. Reductive conditioning at 200 degrees C yields the most active catalyst. Physical origin and consequences of the resulting differences in the reaction behavior are discussed.