The superhydrophilicity of TiO2 prepared by anodization of pure titanium was investigated and the underlying mechanism was explored. The water contact angle of the as-anodized oxide decreases with the conversion voltage and ultraviolet (UV) light illumination, whereas the annealed oxide exhibits further low contact angles regardless of the conversion voltage and UV illumination. The O Is X-ray photoelectron spectroscopy spectra of the oxides have a shoulder peak due to adsorption of hydroxyl groups and the intensity of the peak increases with annealing and UV illumination; these observations suggest that the interaction between the surface of the oxide and the hydroxyl groups is enhanced. (C) 2008 Elsevier B.V. All rights reserved.