A high-temperature, short-contact-time catalytic methane combustor is modeled as a plug-flow tubular reactor including both homogeneous and heterogeneous chemistry. The gas-phase chemistry is modeled with GRI-mech 2.11 and the heterogeneous chemistry is modeled using an elementary 19-step mechanism for combustion of methane on platinum. Calculations are made at a variety of pressures, temperatures, compositions: and catalyst pore sizes to determine their effects on the reactor exhaust compositions. Comparisons are made between results for cases where only homogeneous chemistry is allowed, only heterogeneous chemistry is allowed, and where both mechanisms are allowed. II is found that the homogeneous chemistry in all cases is significantly inhibited by the heterogeneous chemistry, although alone each of these mechanisms takes place on similar time scales. This inhibition is a result of the adsorption of radical species from the gas phase to the surface of the catalyst, which prevents initiation df the gas-phase free-radical chain reactions.