Ti-35V-15Cr,Ti-25V-15Cr and Ti-25V-15Cr-0.4Si alloys were exposed to different temperatures in air (450 - 600 degreesC) for aging times between 0 and 200 h and subsequently tensile tested at room temperature with the surface oxide retained or removed. The influence of an applied tensile stress ( 50 - 200 MPa) during thermal exposure was also investigated. The results showed that post-exposure tensile properties deteriorated with the increase in exposure temperature and time. The decrease in tensile properties resulted from the combination of surface oxidation and microstructural changes. The main change of the microstructure during thermal exposure is the heterogeneous precipitation of a phase on beta grain boundaries. Both increased vanadium content in the alloy and the addition of silicon have shown an adverse effect on alloys' thermal stability. (C) 2004 Kluwer Academic Publishers.