Cobalt oxide (CoO) nanorods were synthesized by annealing CoC2O4 precursor. The nanorods were identified by Transmission electron microscopy (TEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and other methods. The results showed that the nanorods are composed of cubic CoO with diameter of 10-80nm, and lengths ranging from 1 to 3 mum. The mechanism of formation of CoO nanorods was also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.