An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a H2O2/0.1M HCl solution at 80degreesC. The thickness of the gel layer increased almost linearly with the period of the treatment. The gel was transformed gradually to anatase crystal structure after a subsequent heat treatment above 300degreesC. Rutile started to appear above 600degreesC. The titania gel layers exhibited in vitro apatite deposition ability after the gel layers exceeded a minimum thickness (0.2 mum) and was subsequently heated in a proper temperature range (400-600degreesC).