Although titanium has been successful as an orthopedic or dental implant material, performance problems still persist concerning implant-bone interfacial bonding strength. In this study a novel oxygen-diffused titanium (ODTi), fabricated by introducing oxygen into the titanium crystal lattice by thermal treatment, was investigated. The fabricated material is the result of a surface modification made on commercially pure titanium (cp Ti) previously coated with poly(vinyl alcohol) (PVA) by means of a thermal treatment performed at 700 degrees C in an ultra-pure argon atmosphere. The thermal treatment at 700 degrees C led to the formation of an anatase TiO(2) film on the cp Ti surface and a concentration gradient of oxygen into titanium. The surface of the fabricated ODTi consisted of an outer nanometric layer of anatase TiO(2) and an inner nanometric layer of Ti(2)O(x) (x<1) in which the oxygen is in solid solution with the titanium metal. It was found that ODTi possesses in vitro apatite formation ability after being soaked into simulated body fluid (SBF) solution. This apatite formation ability is attributed to the presence of the anatase TiO(2) outermost surface layer and to abundant hydroxyl groups (-OH) formed on the ODTi surface after immersion in SBF.