Highly ordered TiO 2 nanotube arrays were fabricated via electrochemical anodization of high purity Ti foil and Ti thin film coated indium tin oxide (ITO) glass in fluorine containing electrolytes (both aqueous and nonaqueous). The formation of ordered TiO 2 nanotube arrays was affected by the electrolyte temperature and the applied anodization potential. In aqueous electrolyte, the anodization potential exerted significant influence on the formation of TiO 2 nanotube arrays, while little effect from the electrolyte temperature was observed. In nonaqueous electrolyte, the electrolyte temperature markedly affected the TiO 2 nanotube dimensions, while the anodization potential exhibited slight influence in this regard. As a consequence, TiO 2 nanotube arrays with tube diameters ranging from 20 to 90 nm and film thicknesses ranging from several hundred nanometers to several micrometers were obtained. The TiO 2 nanostructures were examined by scanning electron microscopy. Thermal annealing on the anodized Ti induced crystalline formation, which was confirmed by Raman spectroscopy measurement.