The principal objective of this book is to stimulate interest in research that will extend available theory towards a greater understanding of the steps involved in solid-state decompositions and the properties of solids that control reactivities. Much of the activity in this field has been directed towards increasing the range of reactants for which decomposition kinetic data is available, rather than extending insights into the fundamental chemistry of the reactions being studied. The first part of the book (Chapters 1-6) is concerned with theoretical aspects of the subject. The second part (Chapters 7-17) surveys groups of reactions classified by similarities of chemical composition. The final Chapter (18) reviews the subject by unifying features identified as significant and proposes possible directions for future progress.