The oxidation resistance of TiAl at elevated temperatures (> 750degreesC) can be improved by the addition of small amounts of fluorine. The fluorine was applied either by ion implantation or by wetting with diluted HF. The behaviour of fluorine was studied during heating up 1000degreesC at 1h/air. Using non-destructive Ion Beam Analysis (PIGE) the fluorine depth concentration profiles in the near surface region were determined before and after oxidation. Both types of fluorine application show similar results. The temperature dependence of the fluorine depth profiles shows a distinct loss of fluorine between 400degrees and 500degreesC after oxidation for 1 hour. In contrast to this the fluorine amount decreases slowly above 500degreesC up to 1000degreesC. The high fluorine loss is due to the formation of TiF4. The remaining fluorine content offers the possibility for a technical application of the fluorine microalloying effect to improve the oxidation resistance of TiAl-alloys above 750degreesC.