The oxidation behavior of a commercial AlN and (Al2OC)(1-x)(AlN)(x) (x is approximately equal to 0.80), which was obtained by the self-combustion reaction induced by the mechanical activation of the powder mixtures of aluminum metal with natural graphite, was compared in TG-DTA runs. A weight increase due to the oxidation of a commercial ALN began at temperatures above 600 degrees C, followed by a very slow increase with increasing temperature up to 1000 degrees C, whereas that of (Al2OC)(1-x)(AlN)(x) began at temperatures above 700 degrees C, followed by a rapid increase in temperature range from 850 degrees C to 1000 degrees C. The fractional conversion estimated by assuming the weight increase up to 1000 degrees C in TG corresponding to the oxidation reaction of AlN or (Al2OC)(1-x)(AlN)(x) to Al2O3 was about 8% and 23%, respectively. The difference in oxidation reactivity of AlN and (Al2OC)(1-x)(AlN)(x) is discussed.