We report the kinetics of titania nanotube length evolution during anodization of titanium films. Our results show that the nanotube length increase is thermally activated, and governed by voltage-dependent activation energy 0.6 eV <= E-eff <= 1.1 eV expressed by E-eff = E-0-alpha V-anod where alpha is a constant and E-0=1.6 eV is a voltage-independent term. The proximity of E-0 to that of oxygen diffusion in titania suggests that oxygen transport across the titania walls at the pore bottoms is the rate-limiting step. These results provide insights into the mechanism of titania nanotube formation and a framework for their rational synthesis for applications. (C) 2010 Elsevier B.V. All rights reserved.