Titania-supported copper oxide catalysts have been prepared with loadings in the range from 1/3 to 5 theoretical layers and have been tested for the combustion of CO and toluene. Characterisation with XRD, electron microscopy, EDX, TPR, Raman, and XPS gives details about the structure of copper oxide on titania. The results show that dispersed CuOx is formed up to a loading of about one theoretical layer. TPR indicates the formation of two types of dispersed species, which possibly are isolated and polymeric, respectively. XPS data show that the dispersed copper is Cu2+. Th, dispersed species have high catalytic activity for combustion. At higher copper oxide loading, bulk CuO is formed, contributing little to the activity. Comparison of three titania supports with differing surface area and pore size distribution shows that the most favorable is a support with a surface area of about 38 m(2)/g and mesopores in the range 100-800 Angstrom. The longevity of the catalysts was tested in the waste gas from a formaldehyde plant. Deactivation was observed after being on stream for 57 days, and the deactivation is due to sintering of both the support and the copper oxide. Copper oxide on titania is shown to be more active than cobalt, manganese, and iron oxide on the same support.