The range of operating conditions of catalytic combustors focuses attention on low temperature reactivity and high temperature stability of materials. Under lean fuel:air mixtures, catalysts operate at low temperatures and improved reactivity is required. Metal-support interactions improve reactivity as demonstrated with precious metal-ceria systems. However the reasons for enhanced reactivity and the means of optimising the catalysts are still not clear. The need for high temperature stability has led to detailed studies of washcoats, with the mechanism of sintering and the means of prevention now being understood. The demands of still higher temperature operation re-opens the question of materials selection and of combustor design, with two bed systems appearing to offer several advantages. Reassessment of materials in the light of revised design parameters is required.