Boron nitride (BN) nanocrystals have been synthesized by the reaction of Li3N and BBr3 in organic solvent. The experimental results indicated that, at low temperature, hexagonal BN (hBN) is the dominant phase in the sample. The content of cubic BN (cBN) increased with temperature. and it reached a maximum at 480degreesC. As the temperature increased further, the content of cBN decreased, and hBN became the dominant phase again. This phenomenon was discussed briefly in this paper. (C) 2002 Published by Elsevier Science B.V.