The mechanism of growth of anodic titanium oxide in sulphuric acid has been investigated by potentiostatic and potentiodynamic anodizing, electrochemical impedance spectroscopy and transmission electron microscopy. It was found that most of the charge passed during growth is consumed in oxygen evolution at the oxide-solution interface and the measured current relates to the electronic conduction properties of the oxide. Further, it was confirmed that an amorphous to crystalline transition takes place during potentiodynamic growth, and the transition triggers the additional generation of oxygen bubbles that occurs within the oxide. Depending on the growth conditions, the oxygen bubbles can rupture with local re-growth of the film then occurring. (C) 2012 Elsevier Ltd. All rights reserved.