This volume was originally published in 1973. The nature of the non-symmetry determined aspects of ligand-field theory receives inadequate treatment in most texts. This book is concerned with the nature of the ligand-field parameters used to describe the electronic properties of transition metal complexes having cubic and lower symmetries. These radial parameters constitute the non-symmetry-determined part of ligand-field theory. Symmetry-based properties are discussed here only to emphasize the separate roles of splitting factors and symmetry. The reader is assumed to be familiar with the usual approach to ligand-field theory and with elementary group theory.