Auger and LEED measurements have been carried out on the (100) surface of zinc blende SiC. Two different phases of the clean surface, in addition to two kinds of oxygen covered surfaces, have been obtained, identified, and discussed. In the oxygen covered surface, the oxygen is bonded to the Si. The carbon rich phase is reconstructed (2×1), similar to the (100) clean surfaces of Si, Ge, and diamond. The Si topped surface is reconstructed (×) R45°. A model of alternating Si dimers is suggested for this surface.