A series of ZrO2-Al2O3 composite oxides with different ZrO2 contents was prepared by means of a chemical precipitation method using ZrOCl(2)(.)8H(2)O and pseudoboehmite as starting materials. The structures of the samples have been investigated by powder X-ray diffraction (XRD) and transmission electron micrography (TEM), with thermogravimetry differential thermal analysis (TG-DTA and DTG) combined. The results showed that the synthesized materials consisted of ZrO2 and Al2O3 nanosized particles and they existed as amorphous phase in the samples with insufficient contents of ZrO2. The surface areas (S-BET), the pore volumes and the pore distributions were measured by nitrogen adsorption method, and a regular correlation between the pore distributions and contents of ZrO2 was observed. NH3-temperature programmed desorption (NH3-TPD) was used to characterize the surface acidic properties of the samples. The investigation by X-ray photoelectron spectroscopy (XPS) indicated that there were interactions between ZrO2 and Al2O3 in the composite oxides. The synthesized ZrO2-Al2O3 samples were purposively used as the supports for hydrodesulfurization (HDS) process. The sulfided CoMo/ZrO2-Al2O3 catalysts were tested in the HDS reaction of dibenzothiophene (DBT), and the results showed that the sulfided CoMo catalysts supported on the composite oxide with a suitable ZrO2 content performed a higher HDS activity than that supported on alumina. (C) 2004 Elsevier B.V. All rights reserved.