A simple and completely green hydrothermal route has been developed to synthesize copper (Cu) nanocrystallites based on the reduction of CuO by alpha-D-glucose in distilled water at 180degreesC for 24 h. X-ray diffraction, energy dispersive X-ray spectrum and X-ray photoelectron spectroscopy analysis revealed that the as-synthesized product is of pure Cu with face centered cubic structure. Transmission electron microscopy image indicated that the obtained Cu powders consist of uniform, spherical nanocrystallites with the diameters ranging from 320 to 550 nm. Also, the effects of the reaction temperature and reaction time on the phase(s) of the resultant products were investigated, and the possible formation mechanism of Cu in this hydrothermal system was discussed. (C) 2004 Elsevier B.V. All rights reserved.