Physical Methods in Heterocyclic Chemistry, Volume V: Handbook of Molecular Dimensions focuses on bond lengths and angles from X-ray crystallography. This book provides a list of known X-ray structure determinations of molecules and ions that contain heterocyclic rings. Comprised of one chapter, this volume starts with an overview of the use of X-ray diffraction for the study of the geometry of molecules of all types. This text then discusses the three primary reasons for the lack of accuracy in bond lengths and angles determined by X-ray diffraction. This book discusses as well the effect of substitution on the bond lengths and angles in a heterocyclic ring system. The reader is also introduced to the various factors influencing the magnitudes of bond lengths and angles in molecules, which include the degree of hybridization, bond orders, electronegativity, interelectronic repulsion, or the equivalent concepts in terms of which these factors may be expressed. Heterocyclic chemists, biochemists, molecular biologists, and researchers will find this book useful.