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 report successful robust fabrication of zirconium oxide (ZrO2) nanotubes by a one-step, templateless anodizing process. The nanotubes formed perpendicular to the Zr substrate have an open ended array of continuous, well-aligned conformation with ca. 10 nm hole size. The ZrO2 nanotubes with a uniform diameter have great potential for chemical sensing, catalysis, optical emission, and nanoelectrode assembly for batteries and electrochemistry. (C) 2005 The Electrochemical Society.