[en] Among beryllides, beryllium-titanium intermetallic compounds are one of the most promising materials to replace beryllium in future fusion power plants. Due to its chemical stability and improved mechanical properties Ti beryllide has a great potential for fusion applications. In this work we present a detailed study of the oxidation behavior of titanium beryllide under air annealing. High resolution x-ray diffraction combined with ion microbeam techniques were used to follow the evolution of the composition and phases. The microstructure was studied with scanning electron microscopy. The major phases present in the samples were Be10Ti and Be12Ti. During thermal treatments up to 800 ^oC for 1 hour in air, the oxidation occurs preferentially at the beryllide grain boundaries. The stability of the beryllide was followed during the annealing up to 750 ^oC in vacuum, by in situ x-ray analyses and no evidence was found for the formation of the BeO phase during the annealing in vacuum. (author)