The work functions of a number of commercial‐grade silicon‐carbide single crystals have been obtained in high vacuum (p<10−9mm Hg). Low‐energy electron‐diffraction studies have also been made for one of these samples. Surfaces cleaned by argon‐ion bombardment and annealing appeared to contain an excess of carbon. Heating for long periods of time at 1000°C also appeared to produce surfaces which were nonstoichiometric. Oxygen was adsorbed at room temperature on the ion‐bombardment cleaned surfaces with a sticking coefficient of the order of 0.01. Differences in adsorption properties were noted which were probably associated with asymmetry in atomic species on different crystal faces. Work‐function values on opposite faces of any crystal were the same. Hydrogen exposure resulted in work‐function decreases only in the presence of a heated filament. Under similar conditions of ion bombardment and high‐temperature heating, the SiC surfaces appeared to be more stable than those of silicon crystals.