Cyclic oxidation behavior of TiAl implanted with W or Ta was investigated in a flow of purified oxygen at 1200K. The specimens implanted with W or Ta at an acceleration voltage of 100keV or 180keV with a dose of 10(21) ions/m(2) formed adherent alumina scales on the surface, resulting in an excellent oxidation behavior. However, implantation with W with a dose of 10(19) ions/m(2) was insufficient to improve the oxidation resistance of TiAl. The oxidation resistance of the implanted alloys with a dose of 10(19) ions/m(2) was comparable to that of the alloys containing W or Ta I at% or higher, The TiO(2) suppression by doping effect is believed to be a reason for the improvement. As the Z-phase was identified by X-ray diffraction with the specimens which showed excellent oxidation behavior, another reason for the improved oxidation resistance may be a stabilization of Al(2)O(3) layer formed on the specimen by this phase. The ion implantation with high melting point elements has turned out to be a useful surface treatment to improve the oxidation resistance of TiAl without increasing alloy density.