Isotope reference materials are needed to calibrate and validate analytical procedures used for the determination of isotope amount ratios, procedurally defined isotope ratios or so-called δ values. In contrast to the huge analytical progress in isotope ratio analytics, the production of isotope reference materials has not kept pace with the increasing needs of isotope analysts. Three representative isotope systems are used to explain the technical and non-technical difficulties and drawbacks, on one hand, and to demonstrate what can be achieved at its best, on the other hand. A clear statement is given that new isotope reference materials are needed to obtain traceable and thus comparable data, which is essential for all kinds of isotope research. The range of available isotope reference materials and δ reference materials should be increased and matrix reference materials certified for isotope compositions or δ values, which do not exist yet, should be provided.