TiAl coupon specimens were implanted with Fe, Mo, Ta or W ions and then cyclically oxidised with temperature varying between room temperature and 1200 K in purified oxygen under atmospheric pressure. The surface modification by ion implantation was characterised by glancing angle X-ray diffractometry (GAXRD), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). The oxidised specimens were examined by AES, GAXRD, X-ray diffractometry, SEM and EPMA. The implanted elements showed near Gaussian distributions. The oxidation resistance of TiAl is significantly improved by implantation of Mo, Ta or W ions with a dose of 10(21) ions(.)m(-2) at acceleration voltages ranging from 50 kV to 340 kV In general, this effect decreases with a decrease in the ion dose and 10(19) ions(.)m(-2) has no effect. The acceleration voltage has a small influence. The oxide scales consist predominantly of alpha-Al2O3 and are very adherent to the substrates even after 20 cycles (400 h). On the other hand, the implantation of Fe has a little effect. The significant effect brought about by the implantation is attributable to the formation of a thin beta-Ti layer in the modified area, which was confirmed by GAXRD and TEM observations. Therefore, a possible explanation for the improved oxidation resistance is the formation of phase, a solid solution, where diffusion of Al seems much faster than in gamma-TiAI which has an ordered structure. The enhanced Al diffusion results in the formation of a thin but continuous Al2O3-rich layer in the scale during the initial oxidation stage. This layer can be an effective barrier for the subsequent oxidation, and thus allows enrichment of Al2O3, at the scale bottom.