The current volume consists of eight chapters which interweave various aspects of the structure, energetics and reactivity of organic free radicals, all combining pedagogical insights with current research. The first is by Walling in which a personalized overview is given by one of the modern pioneers of the discipline. In the next two chapters, Tsang, and Traeger and Kompe, present key thermochemical and kinetic quantities from the complementary vantage points of the studies of neutral and cationic species. The fourth chapter by Francisco and Montgomery discusses the armamentarium of modern theory as applied to species with unpaired electrons, while the next chapter by Goodman presents the theory, methodology and results from photoacoustic calorimetry, a novel and powerful experimental technique. Martinho Simoes and Minas da Piedade interrelate organometallic and free radical chemistry, while Greenberg and Liebman consider resonance energy and rearrangements as applied to small molecules and enzyme cofactors alike. The volume ends with the chapter by Tanko and Suleman, which describes the surprising and diverse solvent effects which modulate free radical chem- istry. This volume will make it apparent to entry-level graduate students and senior researchers alike that much is known and much remains to be done in both the qualitative understanding and quantitative insights of the chemistry of organic free radicals. Jose Artur Martinho Simoes Arthur Greenberg Joel F. Liebman vii Editorial Advisory Board WESTON T. BORDEN ALAN P.