Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with well-aligned morphology, orientation, and surface architectures remains a significant challenge. Here, we study a simple electrochemical anodizing process to fabricate arrays of titanium (Ti) nanotubes without the use of a template. The nanotubes are formed perpendicular to the metal substrate as an open-ended array in a continuous, well-aligned conformation. The hole size and separation have been found to be dependent on the anodizing voltage and on anodizing time. It was found that the nanotube deposition process had a low faradaic efficiency, and a large fraction of the Ti was transformed into soluble species in the anodizing bath. The TiO2 nanotubes have uniform diameters that make them suitable for electrochemical intercalation hosts for Li+ ions and other applications. (c) 2006 The Electrochemical Society.