The application of polymers at ever-increasing temperatures has given impetus to research on the chemistry of thermal decomposition. In recent years polymers have been used for a variety of high-temperature applications, such as cooking vessels, motor insulation, and re-entry vehicle heat shields. Interest in chemistry of decomposition has been found in such industries as tobacco and grinding-wheels. Because of the vast number of polymers that are available and the variety of applications thousands of papers have appeared in the literature. Rather than give a complete review the purpose of this paper is to give a brief survey of topics that have been emphasized in the author's research, namely kinetics, mechanisms, and gaseous decomposition products at elevated temperatures.