Regular arrays of GaN nanorods have been synthesized by reacting gallium and ammonia using An as a catalyst on a MgO single crystal substrate treated by chemical etching. They were characterized by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED) and X-ray diffraction (XRD). EDX, XRD SAED indicated that the nanorods were wurtzite single crystal GaN. We suggest that regular tactic square shape with steps on the single crystal MgO and discontinuity of the An film may play an important role during the formation of regular arrays of GaN nanorods. (C) 2002 Elsevier Science B.V. All rights reserved.