Ultra-long wire-like single-crystal selenium arrays have been successfully synthesized on a large scale by a solvothermal method starting from SeO2 and ammonia without introducing any templates. The products were characterized by XRD, SEM, TEM and Raman spectra, which revealed that the diameters of the wires were about 180-250nm and the lengths of arrays up to 1-2cm. The possible reaction process of Se wires was discussed. (C) 2003 Elsevier B.V. All rights reserved.