Characterization of oxide scale and α-casing in Ti6Al4V titanium alloy oxidized at 1050, 1150, 1250 and 1340 K for 2, 4, 6, 8 and 12 h in a dynamic oxygen gas atmosphere has been analyzed. the oxide scale exhibited a spalling tendency. Its thickness systematically increased with the temperature and the duration of the oxidation. at a later stage the scale exhibited a catastrophic growth due to the increased porosity. the oxygen stabilized α-phase and its volume fraction as well as its hardness decreased with the distance in the metal matrix (α-casing). Estimated oxygen diffusion coefficients based on the hardness profiles across α-casing were 7.0 x 10-14, 8.5 x 10-14, and 1.2 x 10-13, 1.8 x 10-13 m2/s at 1050, 1150, 1250, and 1340 K, respectively. Similarly, the overall activation energy for diffusion of oxygen in the alloy was 105 kJ mol-1. EDS analysis across α-casing in the internal oxidation zone revealed sharp concentration wells for Ti and Al. Titanium concentration decreased and that of aluminum increased in these wells.