The effect of carbon additions on microstructure and mechanical properties of alloys with different levels of oxygen was studied in β titanium alloys of the general composition Ti-25V-15Cr-2Al (all compositions are in wt% unless otherwise indicated). The microstructures were studied using optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that titanium carbides with vacancy-ordered structure formed in all alloys with C additions of over 1000w.p.p.m. Grains were refined by carbides. Wavelength-dispersive X-ray (WDX) analysis showed that oxygen was much higher in carbides than in β matrix. After long-term exposure at 550 o C α precipitation was significantly reduced in samples with titanium carbides compared with those without. A significant improvement in room temperature tensile ductility was achieved by the addition of carbon to the alloys. Elongations of ~10% were obtained in samples which were exposed at 550 o C for 500h following heat treatments at 1050 and 700 o C.