Alloys of Ti39.4Al10V (at.%) that consisted mainly of ordered beta-Ti, gamma-TiAl and alpha(2)-Ti3Al phases were oxidized at 700, 800, 900, and 1000degreesC in air. The oxide scales formed consisted largely of an outermost, thin TiO2 layer, an outer, thin Al2O3 layer, and an inner, very thick (TiO2+Al2O3) mixed layer. Vanadium, which was uniformly distributed throughout the oxide scale, harmfully decreased oxidation resistance, and made thick, nonadherent scales owing to the formation of low melting compounds of V-oxides. The oxidation progressed via the outward diffusion of Ti, Al and V ions, and the concurrent inward transport of oxygen.