[en] Fore more than thirty years the International Atomic Energy Agency (IAEA), through its Analytical Quality Control Services (AQCS) programme, has been assisting Member States' laboratories to maintain and improve the reliability of their analyses by organizing intercomparison exercises and by preparing and distributing biological, environmental and marine reference materials. The catalogue consists principally of two parts: The list of all available IAEA reference materials grouped into five categories: reference materials for radionuclides; reference materials for trace, minor and major elements, including oxides; reference materials for stable isotopes; reference materials for organic contaminants and methyl mercury containing materials. Lists of all available IAEA reference materials sorted by analytes. In addition information on recommended half-life data and suppliers of radioactive sources is provided. Planned intercomparisons are advertised and request forms for participation in intercomparisons are included. Forms for ordering reference materials, quality control spectra for gamma-spectrometry on diskettes and AQCS related publications are also provided