Catalytic combustion is useful to avoid emission of nitrogen oxides, to combust fuel gas of different calorific levels, and to combust low contents of badly smelling or hazardous gaseous compounds. After dealing with some characteristics of catalytic combustion it is argued that catalytic combustion to a final temperature lower than about 800 degrees C calls for a rapid transport of thermal energy out of the reactor. A fluidized bed in which combustion has been successfully performed is dealt with as well as a reactor filled with metal bodies sintered to each other and to the wall of the reactor. To achieve a sufficiently high catalytically active surface area a thin layer of silicone rubber is applied to the surface of the metal bodies and subsequently pyrolyzed to a highly porous layer of silica. To raise the thermostability alumina can be added to the silica layer. To establish a final temperature above 900 degrees C the homogeneous gas-phase combustion can be ignited by a solid catalyst or the reaction can be performed completely catalytically. Since the combustion reaction proceeds very rapidly at elevated temperatures, a large gas how can be utilized, which calls for a reactor exhibiting a low-pressure drop. For catalytic combustion monoliths and gauzes are appropriate. The chemical composition of ceramic and metallic monoliths is dealt with as well as the cell densities and wall thicknesses of commercial monoliths. The application of active components to the surface of the walls of monoliths is subsequently discussed. Since monoliths do not allow radial mixing, a homogeneous gas mixture has to be fed to the monolith to prevent very high temperature levels moving randomly over the channels of the monolith and deactivating the catalyst. With monoliths in gas turbines often catalytic ignition is used. To limit the temperature a fraction of the fuel feed is injected into the homogeneous combustion chamber. A number of alternatives of transporting the fresh fuel to the homogeneous combustion zone is mentioned. The cause of the catalyst temperature being higher than that of the gas flow is dealt with as well as the low volatility at elevated temperatures required for the catalytic components. Selection of the catalytically active materials is discussed and the procedure to bring the gas flow at the light-off temperature of the catalyst. Monolithic combustors used in radiant heaters display often an oscillatory behavior. After dealing with the cause of the oscillations, prevention by means of a flame arrestor is mentioned.