Titania nanotube arrays were fabricated by anodic oxidation of titanium foils in HF solution, which were then treated in NaOH solution or Ca(OH)(2) solution to make them bioactive. The ability to form apatite on the as-treated samples was examined by immersion tests in simulated body fluid combined with Enviromental Scanning Electron Microscopy (ESEM), Energy Dispersive X-ray Analyzer (EDAX) and X-ray diffractometer (XRD) investigations. The results show that the presence of titania nanotube arrays on titanium surface could shorten the activation time of NaOH-treated from 24 h to 30 min, and induces the growth of nano-grain calcium titanate on the top edge of the nanotube wall in Ca(OH)2 solution. During the subsequent in vitro immersion in a simulated body fluid, the nano-grain calcium titanate, in turn, induced the formation of apatite phase. It is expected that titanium with such titania nanotube can be used in clinical orthopaedics. (C) 2007 Elsevier B.V. All rights reserved.