The highly ordered TiO2 nanotube arrays were fabricated by potentiostatic anodization of Ti foils in fluorinated dimethyl sulfoxide (DMSO). TiO2 nanotube arrays are formed using a 40 V anodization potential for 24 h, with a length of 12 mu m, diameter of 170 nm and aspect ration of about 70. The asprepared nanotubes are amorphous, but can be crystallized as the heat treatment temperature increases. Anatase phase appears at a temperature of about 300 degrees C, then transforms to rutile phase at about 600 degrees C. After heat treatment at 500 degrees C and soaking in SBF for 14d, a thick apatite layer of about 13 mu m covers the whole surface of TiO2 nanotube arrays, indicating their excellent in vitro bioactivity, which is mainly attributed to their high specific surface area and the anatase phase. (c) 2008 Elsevier B. V. All rights reserved.