Nanocrystalline titanium diboride (TiB2) has been prepared by the reaction of TiCl4 with NaBH4 in the temperature range of 500-700 degreesC in an autoclave. X-ray powder diffraction (XRD) patterns can be indexed as hexagonal TiB2 With the lattice constants of a = 3.032 and c = 3.229 Angstrom. Transmission electron microscopy (TEM) image shows particle morphology, with average size of 15 nm for the powder obtained at 600 degreesC. Selected area electron diffraction (SAED) pattern confirms the prepared hexagonal TiB2. The oxidation behavior of TiB2 is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). (C) 2004 Elsevier Ltd. All rights reserved.