Recent advances in both experimental techniques and theoretical methodologies have meant that increasingly sophisticated studies concerning the formation, structures, energetics and reaction dynamics of state- or energy-selected molecular ions can now be performed. In order to better serve the ion chemistry and physics community, each volume of this series is dedicated to reviewing a specific topic, emphasizing new experimental and theoretical developments in the study of ions. The Wiley Series in Ion Chemistry and Physics will help stimulate new research directions and point to future opportunities in the field of ion chemistry and physics. This volume, the fifth in the series, concentrates on the important area of organic ions. Our understanding of these ions has been significantly improved over the last decade due to both theoretical and experimental advances, and it is now routinely possible to calculate organic ion structures by ab initio molecular orbital methods with very high precision. At the same time, the experimental tools used to study organic ions have become much more refined. This volume provides a timely overview of some of the key approaches which are currently producing such important results in the study of negative ions, and contains seven chapters written by acknowledged experts in the field. It will be of great interest to both experts and newcomers, both of whom will benefit from the in-depth discussion of the latest methods and results.