1) Westfälische Wilhelms Universität, Institut für Mineralogie, 48149 Münster, Germany, 2) Max Planck Institute for Chemistry, PO Box 3060, 55020 Mainz, Germany, 3) Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK, 4) Department of Earth Science and Engineering, Imperial College, London SW7 2AZ, UK, 5) Institut für Geologie und Mineralogie, Universität zu Köln, 50674 Köln, Germany, 6) Department of Chemistry, University of Otago, Dunedin, New Zealand, 7) School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK (8) Department of Earth and Ocean Sciences, University of British Columbia, British Columbia, Vancouver, Canada (9) Present address: Steinmann Institut, Universität Bonn, 53115 Bonn, Germany (10) Present address: Department of Geology, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA Geostandards and Geoanalytical Research (2013), V37(1), pp5–17, doi: 10.1111/j.1751-908X.2012.00175.x A Common Reference Material for Cadmium Isotope Studies -- NIST SRM 3108 Wafa Abouchami (1, 2), Stephen J. G. Galer (2), Tristan J. Horner (3), Mark Rehkämper (4), Frank Wombacher (5, 9), Zichen Xue (4), Myriam Lambelet (4), Melanie Gault-Ringold (6), Claudine H. Stirling (6), Maria Schönbächler (7), Alyssa E. Shiel (8, 10), Dominique Weis (8) and Philip F. Holdship (3) Research into natural mass-dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC-ICP-MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double-spike techniques, sample-calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in-house Cd solutions used as zero-delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round-robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in-house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero-delta’ in future studies.