Anatase phase of TiO2 has been shown to have very good biocompability. It was frequently observed on Ti surfaces after anodizing and thermal annealing treatments. Recently, it was shown that TiO can lead to the formation of anatase. In this report the mechanisms of the Ti to TiO and the TiO to anatase phase transitions in anodizing and annealing treatments of Ti have been studied by transmission electron microscopy. Ti thin films of two strong textures were first grown on the (001)(NaCl) substrates. In addition to amorphous TiO2, the anodization treatment caused the formation of TiO with an orientation relationship of (11 (2) over bar0)(Ti)//(220)(TiO) with Ti. The subsequent thermal annealing treatment caused the TiO to anatase transition with an orientation relationship of {200}(TiO)//{200}(A). Pure anatase film was prepared by this method. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.097203jes] All rights reserved.