High purity boron carbide nanowires with mean diameter of around 50 nm and with typical lengths of several tens to hundreds of micrometers were produced in thermal evaporation of B/B2O3/C powder precursor under argon atmosphere without the presence of catalyst. XRD, EELS and high-resolution transmission electron microscopy revealed the single crystallinity of these nanowires. A vapor solid (VS) mechanism, where the carbothermal reductions of boron oxide (B2O3) or dimeric boron mono-oxide (B2O2) vapors occur, was employed to explain the growth. These refractory semiconductor nanowires of boron carbide could be ideal for high temperature applications in materials and electronics as well as studying ID nanoscale transport phenomena. (C) 2002 Elsevier Science B.V. All rights reserved.