The oxidation property of a Ti-33.5 mass%Al-2.5 mass%Mn intermetallic compound prepared by a reactive-sintering process was studied at 1223 K in air in comparison with that by a melt process. The reactive-sintered alloy had been found to have superior oxidation resistance to the melted one. The oxidation scale of the former was suggested to be adhesive, for example, owing to the presence of fine alumina particulates and/or pores which contribute to pegs. The fine alumina particulates were developed by breaking up of the oxide layer along prior particle boundaries during the reactive-sintering process.