Abstract The interaction of oxygen with NiAl(110) has been studied using AES and LEED techniques. The OKVV Auger intensity curve shows two linear parts with clear breaks at 15 and 90 L. After 90 L the oxygen Auger signal increases very slowly. Saturation is observed above an oxygen exposure of 300 L. Oxygen adsorption occurs in two different phases: at exposures smaller than 15 L only a surface chemisorbed phase on the top Al atoms is formed, while at higher exposures a subsurface phase is formed having bulk-like oxide properties. There is no evidence for any nickel-oxygen interaction. Oxygen uptake stops after formation of an A1 2O 3 thin-film layer, which prevents further oxygen transport into the bulk.