Titanium surface was covered with thin layers of titanium monocarbo-nitride, Ti(C,N) and nitrogen-rich a-titanium, after a titanium specimen was heat-treated at a temperature between 1388 and 1573 K in a graphite cup in an atmosphere of pure nitrogen. The total thickness of those layers increased in accordance with the parabolic law when both temperature and time of the heat treatment increased. The parabolic rate constants was described as k = 4.83 × 10-6 exp (-178000/RT)m2/s using Arrhenius’ equation. Vickers hardness of the Ti(C, N) layer remained at approximately 2000 but that of the a-titanium layer gradually decreased from 1500 to 500, as the distance from the surface increased. The carbo-nitridetreated titanium exhibited excellent resistances in wear and corrosion compared with those of pure titanium.