We explore the so-called „non-traditional“ stable isotopes, of which the minor shifts by isotope fractionation have been made detectable by multicollector ICP-mass spectrometry. These are for example the elements lithium, magnesium, silicon, calcium or iron. • Why do isotopes shift their relative abundances? Principles of mass-dependent isotope fractionation. Isotope fractionation during precipitation, mineral dissolution, weathering, uptake by higher plants, biomedical applications, the hydrosphere, and formation of the planets. Basics of MC-ICP-mass spectrometry: sample preparation, ionisation, ion optics and mass separation, detection systems, data evaluation.