This major textbook offers a new conceptual framework for metamorphic petrology, based on progress made over the past 20 years. During this period, the subject has undergone drastic changes, owing partly to the progress of thermodynamic investigations of metamorphic reactions and of the actual conditions of metamorphism under which such reactions occur, and partly to intensive field studies based on petrological, tectonic, geological, thermobarometric, geochronological and geophysical methods. Metamorphic petrology starts with detailed discussions of progress in the study of the general principles of metamorphic petrology. Thus, the following topics are discussed: prograde and progressive metamorphism, P-T-t paths, thermal peaks, classifications and thermodynamic characteristics of metamorphic reactions, the relations of isograds to thermal-peak isotherms and isobars, the polychronous origin of isograds, internal and external buffering, and infiltration of externally derived fluids. Then discussions proceed to more traditional petrological subjects, such as metamorphic facies, a P-T-t ratio classification of metamorphic regions, and the tectothermal evolution of metamorphic belts. Also discussed is the change with temperature and pressure of the paragenetic relations of minerals and the chemical compositions of solid-solution minerals.