The mechanical properties of the oxide layers developed at elevated temperature on three vanadium-free titanium alloys of interest for biomedical applications were investigated by means of the nanoindentation technique. The as-received alloys (Ti-13Nb-13Zr, Ti-15Zr-4Nb and Ti-7Nb-6Al) and their oxide scales formed by reaction with air at 750 degrees C for several oxidation times were analysed comparatively. In particular, the hardness and the Young's modulus exhibit larger values for the thermally oxidized alloys than for the untreated specimens. However, the Ti-7Nb-6Al alloy shows a different tendency to that of the TiNbZr alloys, which seems to be related to a different oxide layer growth as a function of the oxidation time.