Bulk quantities of self-assembled, functionalized nickel oxide nanowires (lengths <= 20 mu m; mean diameter 25 nm) have been grown by a novel electrochemical method consisting of multistep oxidation of Ni-Cr alloys in high-temperature, pressurized water. Nanowires form when growth results in a deficit of OH- in the electrolyte ahead of the growing NiO. The compositional gradient breaks up the planar NiO/water interface into a cellular interface, resulting in the growth of NiO nanowires. (c) 2005 The Electrochemical Society.