A series of palladium-ceria-supported catalysts prepared by the sol-gel method are characterized and their catalytic results are reported. It was found that the addition of ceria to alumina produces a highly dispersed catalyst when compared with their zirconia counterparts. However, the catalytic activity of the ceria zirconia series is higher, essentially due to the larger particle size of palladium. This result can be attributed to the structure-sensitive reaction of the combustion of methane. (C) 2004 Society of Chemical Industry.