Metastable cubic tantalum nitride (TaN) nanocrystals have been firstly direct synthesized by dc arc discharge and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) techniques. The average grain size of cubic TaN nanocrystals is about 5-10 nm. The influence of N-2 pressure on the assynthesized metastable cubic TaN is studied and it is found that lower N-2 pressure is favorable for the formation of metastable cubic TaN. The growth mechanism of metastable cubic TaN was discussed. This method may be suitable for a direct preparation for mass production of TaN nanocrystals. (c) 2007 Elsevier B.V. All rights reserved.