Alloys of Ti-15Mo-5Zr-3Al(wt%) were oxidized in air between 700 and $900^{circ}C$. It was found that the oxidation resistance is much better than that of either commercially available pure Ti-6Al-4V(wt%) alloys. The oxide scales were primarily composed of thick Ti-ox-ides which were formed by the inward diffusion of oxygen from the atmosphere. At higher temperatures a thin $alpha$-$Al_2O_3$ layer was formed on Ti-oxides owing to the outward diffusion of Al from the base alloys. Molybdenum, the noblest metal among the alloy components, was predominantly present behind the oxide-substrate interface. Zirconium, an oxygen active metal, was present at both the oxide layer and the substrate.