We investigated the electronic states of titanium oxide nanotubules (TiOx-NTs) by using field induced surface photovoltage spectroscopy (FISPS). Compared with common TiO2 P25 nanocrystals, new surface photovoltage response hands extending to 550 nm were found under the effect of external electric field. Based on the principle of FISPS, these responses were ascribed to the surface state transitions. X-ray diffraction (XRD) indicated that the crystalline structure changed remarkable during the hydrothermal synthesis process. The existence of oxygen vacancies contributing to the surface states was further confirmed by the sub-band gap photoluminescence. (C) 2003 Elsevier B.V. All rights reserved.