Free radicals, which are key intermediates in many thermal, photochemical and radiation processes, are important for a proper understanding of fundamental natural processes and the successful development of organic syntheses. After about one decade volume II/18 serves as a supplement and extension to volume II/13 and covers rate constants and other kinetic data of free radical reactions in liquids. Furthermore II/18 contains new chapters on reactions of radicals in excited states and of carbenes, nitrenes and analogues. Selected species in aqueous solutions for which other compilations are available were deliberately omitted as before, and for the same reason electron transfer equilibria of organic radicals were not covered.