This book collects data pertaining to diagrams of quaternary systems based on II-VI semiconductor compounds. It illustrates up-to-date experimental and theoretical information about phase relations based on II-VI semiconductor systems with four components. It critically evaluates many industrially significant systems presented in two-dimensional sections for the condensed phases. Each quaternary database description includes the diagram type, possible phase transformations and physical-chemical interactions of the components, thermodynamic characteristics, and methods for equilibrium investigation and sample preparation.