Chemical and Biological Generation of Excited States discusses major aspects of chemical and biological generation of electronic excitation. This book is organized into 11 chapters that focus on both chemi- and bioenergized processes. This book first discusses some of the fundamental aspects of the description of excited state behavior in condensed media. It then examines the field of gas-phase dioxetane chemiluminescence both by itself and in relation to solution-phase studies. The presented analysis is based on statistical mechanics and supported by a very simple limiting case calculation. Chapter 4 describes the state-of-the-art of how excitation yields are determined experimentally in chemienergized processes. This is followed by a discussion on activation parameters and stability trends, focusing on solution-phase data. Chapters 6 and 7 examine solution-phase chemiluminescence resulting from high-energy electron-transfer reaction, often involving aromatic radical ions, and the mechanism of excitation step. The next chapters cover the generation of electronic excited states in bioluminescence and the evaluation of luminescent oxidation mechanisms using oxygen tracers. The chapters also explain the formation of electronically excited products in dark biological processes and the mechanism of chemiexcitation as it relates to redox metabolism. Specific examples of biological oxygenation reactions yielding luminescence are also presented. Furthermore, this book discusses the concept and applicability of chemiluminigenic probing for the quantification and differentiation of oxygenation activities in mammalian phagocytes. The concluding chapter is devoted to the possible formation of singlet oxygen in various systems and processes that mimic singlet oxygen reactions. The book intends to attract young scientists as well as established research workers to broaden the horizons of this rapidly growing and potentially very important field.