The interaction of oxygen with sulfur‐covered nickel and nickel sulfide surfaces was investigated by AES. For the adsorbed sulfur the interaction appears to proceed via an intermediate step prior to the removal of sulfur; a proposed mechanism of interaction is presented. This interaction is dependent on oxygen pressure. Under certain conditions three‐layer oxide can form on a buried sulfur layer and this oxide is destabilized by the presence of sulfur. Oxidation of the nickel sulfide appears to be similar to that of the adsorbed‐sulfur‐on‐nickel system with regard to oxide buildup. The effect of temperature on these processes is discussed.