CeO2-ZrO2 solid solutions have been prepared by precipitation of the corresponding hydroxides, They were calcined and aged at various temperatures and characterised by X-ray diffraction measurements, BET and TPR measurements as well by their activity in methane combustion. The Ce0.67Zr0.33O2 Solid exhibited the best thermal stability, the highest oxygen mobility and the best catalytic activity after ageing at 1000 degrees C. It has been used to support active phases like platinum and manganese oxide. The fresh Pt/Ce0.67Zr0.33O2 catalyst was much more active than the corresponding Pt/Al2O3 solid although a deactivation on stream was observed in the 200-500 degrees C temperature range. Nevertheless, the promoting effect of the Ce0.67Zr0.33 support disappeared after ageing at 1000 degrees C. In the case of MnOx supported onto the Ce0.67Zr0.33O2 Solid Solution the activity of the fresh solid is similar to that of the MnOx/Al2O3 catalyst, After ageing at 1000 degrees C, the solid solution is decomposed, the BET area dramatically decreased and the catalytic properties almost disappeared. As far as temperature applications exceeding 1000 degrees C are concerned, the CeO2-ZrO2 solid solutions are not suitable supports for the catalytic combustion of methane. (C) 2000 Elsevier Science B.V. All rights reserved.