A researcher trying to predict or interpret spectra of transition metal ionsin possible laser host materials is confronted with a variety of different methods of describing the same physical situation. This book provides a systematic approach to the applied theory of crystal-field interactions of transition metal ions in 49 crystalline hosts that are or show promise of being good laser materials. The tables that make up the main part of the book present the experimentally determined parameters of the 3dN, 4dN, and 5dN transition-metal ions in the second, third, and fourth ionization states. These parameters have been converted to Slater and crystal-field parameters. The book is a source for research workers in laser development and in crystal-field theory, and for graduate students of solid state chemistry and physics.