Process chemistry spans a broad range of research topics, each of which is essential to an understanding of oil shale retorting processes and of the way which these processes may impact the environment. Oil shale retorts of various types and sizes, from above ground to modified in situ, have been operated for several years. Yet the fundamental chemical reactions that take place when shale is retorted, the formation and destiny of heteroatoms of nitrogen, sulfur, arsenic and heavy metals, the effects of process parameters on the chemical and physical properties of the product oil, and the relationships between process parameters and downstream contaminants in the water and the spent shale are but marginally understood. Much additional effort is needed, moreover, to establish a capability for modeling the reaction kinetics that govern various retorting processes.