The inducing effect of halide species on the formation of cubic boron nitride (cBN) in hydrothermal solutions was investigated. The results indicated that both Cl- and F- played an important role in promoting cBN and suppressing hBN, and the inducing effect of the latter was much stronger than that of the former. Although the inducing effect was firstly observed in the phase-selective synthesis (PSS) method, by which pure cBN micro-crystals were synthesized, it was also applicable in both high-temperature in-situ reaction (HTISR) and conventional hydrothermal synthesis (CHS) methods. When the concentration of Cl- and F- was high enough, pure cBN could also be expediently synthesized by the CHS method. (C) 2009 Elsevier B.V. All rights reserved.