CeO2 nanotubes with diameters of 10-15nm and length of 150-200nm have been successfully synthesized by a sonochemical method under ambient air in alkali aqueous Solution without any template. It was found that both high alkali concentration and ultrasound irradiation played critical roles for the formation of the nanotubes. The crystalline structure and dimensions of the nanotubes were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The UV-visible absorption spectroscopic measurement results showed that the products had conspicuous quantum size effects. (c) 2005 Elsevier B.V. All rights reserved.