Continuous hydrothermal synthesis in supercritical water (supercritical synthesis) is a method to prepare metal oxide nanoparticles rapidly and continuously using supercritical water. Highly crystallized nanoparticles of homogeneous complex metal oxides as well as single metal oxides Could be produced easily by the supercritical synthesis. Ceria-zirconia mixed oxide is widely used as oxygen storage material, for example, in the three-way catalysts for the clean LIP of automotive gases. Ceria-zirconia mixed oxides were prepared by the new supercritical synthesis method and also by the conventional co-precipitation method. The characteristics in oxygen storage capacity (OSC) of ceria-zirconia mixed oxide prepared by the supercritical synthesis were compared with those by the co-precipitation method. It was confirmed through physical characterizations with N-2 adsorption, SEM, TPR and O-2-uptake that the supercritical synthesis could lead to ceria-zirconia mixed oxides with higher thermal stability and better OSC due to its morphology. (c) 2006 Elsevier B.V. All rights reserved.