The transition from sp(2) to sp(3) hybridization in boron nitride has been induced in plasma. Nano-crystals of cubic boron nitride (cBN) have been synthesized by direct current arc discharge method using hexagonal boron nitride (hBN) as the starting material. The characterization of the as-grown powders is carried out by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. It has been shown that cBN and hBN grains with 20-60 nm in size co-exist in the powders. A reaction route of sublimation-re-hybridization-crystallization had been put forward to explain the mechanism of the hybridization transition and the growth of cBN by this method. (C) 2004 Elsevier B.V. All rights reserved.