Six authoritative reviews by leading researchers present the major advances that have occurred in the conformational analysis of medium- sized heterocycles (i.e. eight-to eleven-membered heterocycles). The papers emphasize new computational and photoelectron spectroscopic methods, are extensively illustrated, and reveal hitherto unappreciated major advances. Among the points of interest is that medium-sized ring heterocycles may have well-defined conformational minima with substantial barriers for conformational change. Attention is also called to the unique geometries in such systems that provide opportunities for transannular juxtapositions. This book fills an important gap in the review literature and points to unique and important applications.