An X-ray investigation of the compounds aluminum carbide, Al4C3, and aluminum oxycarbide Al4O4C yielded data which differed from that in the A.S.T.M. files. The aluminum carbide pattern was similar in many ways to that calculated by Stackelberg and Schnorrenberg (Z. Physik. Chem., Sect. B, 27, 37 (1934). Minor differences occurred in the Al4O4C pattern.