Catalytic methane combustion was studied over the palladium single crystals Pd(111), Pd(100) and Pd(110). Under lean reaction conditions at 600K (O2:CH4=10:1), stoichiometric palladium oxide was formed with an increase in surface area by a factor of approximately two. The oxide phase formed a “cauliflower-like” surface structure composed of approximately 4nm sized semispherical oxide agglomerates. This oxide structure was independent of the original metal single crystal orientation. The turnover rates over the oxide structure starting with metal single crystals were 0.7s−1 on Pd(111), 0.9s−1 on Pd(100) and 0.9s−1 on Pd(110) at 600K, 160Torr O2, 16Torr CH4, 1Torr H2O and N2 balance to 800Torr, suggesting that the methane combustion reaction is independent of the initial structure of the catalyst. Methane combustion on palladium single crystals experienced an activation period in which the initial turnover rates based on the initial Pd surface area were about 1/8–1/4 of the steady-state rates determined based on the oxide surface area. This activation period was caused by the slow oxidation of palladium single crystals and concomitant surface area increase during reaction. The increase in surface area happened mostly in the first 10min of reaction. Carbon dissolution into the crystal was not found during methane combustion under reaction conditions in excess oxygen.