Among small inorganic molecules there are some which are important for most technicalcombustion processes, namely H 2 , O 2 , CO, NO, and others. Reactions of H 2 , O 2 , and the radicals which they form, such as H, O, OH, and HO 2 , play an essential part in the ignition and combustion of hydrocarbon and other fuels. The most important elementary steps in the H 2 -O 2 -CO system are discussed. Reactions of nitrogen-containing components can give rise to NO formation; elementary steps which break N-N bonds, and other reactions which lead to the formation of N-N bonds are discussed. Reactions of CS 2 , COS, and H 2 S are included as examples of reactions of sulfur-containing substances. Finally, some recent results of reactions with fluorine atoms are mentioned.