RuO2 nanotubes with diameters of 15-25 nm and up to 3 pm in length have been prepared by the thermal decomposition of Ru-3(CO)(12) inside alumina templates. The RuO2 (110) planes grow along the long axis of the straight crystalline nanotubes. The growth of these fluorescent nanotubes appears to have proceeded via mononuclear ruthenium carbonyl intermediates (see Figure).