The effect of aluminium, tungsten, tantalum and hafnium on the oxidation behaviour of titanium was investigated. Model alloys were oxidized in air for 5000 h at 650°C. All alloying elements decreased oxide growth and oxygen dissolution in the metal; tungsten was the most efficient. The oxygen diffusivity decreased with aluminium. Tungsten enhanced the formation of Ti$_2$N at the oxide/metal interface which decreased oxygen dissolution in the alloys. Experiments in Ar-20%O$_2$, where Ti$_2$N could not form, confirmed the major role of nitrogen on the oxidation resistance of tungsten-containing alloys. The ternary model alloy Ti-10Al-2W outperformed the high-temperature alloy Ti6242S.