US nanocrystallites were synthesized by the hydrothermal method and characterized by XRD, TEM, and XPS, respectively. Different coordination agents were chosen as the template to investigate their effects on the product morphology. It was found that the US nanocrystallites displayed a rod-like shape when ethylenediamine or methylamine were employed as the template. In contrast, only nanoparticles of US were observed when ammonia or pyridine were used. Based on our experimental results, a complex structure-controlling mechanism is proposed. (C) 2004 Elsevier B.V. All rights reserved.