The investigated gamma-TiAl based alloy TNM-B2 belongs to the group of intermetallic materials. Due to their low density, their high specific strength and stiffness at high temperature and their good creep resistance, they are of great interest for the aerospace industry. A remarkable weight reduction could be achieved by using them instead of heavy Ni base superalloys. Apart from their excellent high temperature properties TiAl alloys show low ductility at room temperature. Ductility further decreases due to oxidation. Therefore, the intention of this work was to characterize this temperature dependent reduction of ductility caused by oxidation. Differential scanning calorimetry and thermal gravity (DSC/TG) measurements were conducted in order to obtain the oxidation onset temperatures and the oxide film growth rates. Oxidation products were detected by X-ray diffraction. SEM investigations and secondary ion mass spectrometry (SIMS) measurements were performed to analyse the thickness of the oxide film and the depth of the O diffusion zone. The fracture strains obtained by the tensile tests are quantitative values for the ductility. Tensile tests of different oxidised samples were conducted at room temperature, 300 and 650°C. Microscopic investigations of the broken specimens led to further information about the occurring failure mechanisms.