A simple and efficient electrochemical route was developed for the synthesis of CuO nanocrystals with different shapes using aqueous sodium nitrate electrolyte and Cu sacrificial anode in an undivided cell at a constant current mode under room temperature. The composition, shape and microstructure of the product were characterized by XRD, TEM, HRTEM and SAED. The TEM results indicated that the shape and size of CuO nanocrystals could be conveniently controlled by varying current density or electrolytic solvent. Mono-disperse and almost uniform CuO nanorods or nanospindles could be obtained at low current density, while high current density could result in the formation of irregular-shaped crystals. Compared with pure water solvent, H2O EtOH mix-solvent is more beneficial for the formation of CuO nanorods thinner in diameter. The possible formation and growth mechanism of CuO nanocrystals via the electrochemical route was also proposed. (C) 2007 Elsevier B.V. All rights reserved.