We have prepared titania aerogel and titania-coated silica aerogel incorporating Au nanoparticles. While the sizes of the Au particles in the titania aerogel considerably increased upon calcination at 673 K, those in the titania-coated silica aerogel were almost unchanged. As a consequence. the latter composite aerogel showed higher activity for oxidation of CO. These results indicate that the size of the An nanoparticles and the loading amount of Au can be independently controlled by using the titania-coated silica gel support. (C) 2004 Elsevier B.V. All rights reserved.