This classic textbook is an introduction to the systematics and the use of stable isotopes in geosciences. It is subdivided into three parts: i) theoretical and experimental principles, ii) fractionation processes of light and heavy elements, iii) the natural variations of geologically important reservoirs. Since the publication of the previous edition advances in multicollector-ICP-mass-spectrometry allow precise measurements of new isotope systems. In this new edition therefore, 42 elements with resolvable natural variations in isotope composition are discussed. New findings from non-traditional isotope systems have been incorporated. Many new references have been added, which enable quick access to recent literature. This classic textbook is an introduction to the systematics and the use of stable isotopes in geosciences. It is subdivided into three parts: i) theoretical and experimental principles, ii) fractionation processes of light and heavy elements, iii) the natural variations of geologically important reservoirs. Since the publication of the previous edition advances in multicollector-ICP-mass-spectrometry allow precise measurements of new isotope systems. In this new edition therefore, 42 elements with resolvable natural variations in isotope composition are discussed. New findings from non-traditional isotope systems have been incorporated. Many new references have been added, which enable quick access to recent literature. Jochen Hoefs has been working in the field of stable isotope geochemistry of the elements hydrogen, lithium, carbon, oxygen and sulfur since 1965. His main scientific interests include the stable isotope geochemistry of the mantle and lower crust, the genesis of basaltic and granitic magmas, water/rock interactions under hydrothermal conditions, the history of the ocean and the atmosphere and the application of stable isotopes to environmental problems. He has published about 150 scientific papers, mostly in international journals.