High-purity carbon nanotubes were synthesized using a novel catalyst: tungsten-containing complex (C14H10O7W).The carbon nanotubes have a multiwalled structure that is hollow on the inside and a clean surface without carbonaceous particles. The carbon nanotubes have average diameters in the range Of 20-60 nm and lengths of 30 mu m. Transmission electron microscopy analysis reveals that the inner graphite sheets of these nanotubes are highly crystallized, but the outer graphite sheets are defective. The microstructures of the carbon nanotubes produced from C14H10O7W, tungsten hexacarbonyl [W(CO)(6)], and iron pentacarbonyl [Fe(CO)(5)] were analyzed using high-resolution transmission electron microscopy. We demonstrate that the tungsten-based catalyst can effectively be used to produce the carbon nanotubes. C 2005 American Vacuum Society.