New composites of Ti-Cr-N system were synthesized using a high power millimeter-wave heating method. Ti-Cr-N composites were synthesized from the powder mixtures containing metallic Ti and Cr2N under nitrogen atmosphere by 28 GHz millimeter-wave radiation. The composites consisted of (Ti,Cr)N, Cr2N with some amount of metallic Cr, and their hardness ranged from 9 GPa to 15 GPa, depending on the nitrogen pressure during sintering. In these composites, quite high oxidation resistance was found from their small weight gains less than 5 g/m(2) in oxidation experiment in air at 1000 degreesC for 60 min.. It was also indicated that a high pressure nitrogen environment is advantageous for the millimeter-wave syntheses of nitride composites with high oxidation resistance.