The role played by geochemical reference materials in establishing and maintaining a quality control/quality assurance program in a geochemical/assay laboratory is discussed. It includes the development of in‐house reference materials and their characterization with reference to internationally recognized reference materials. It also concerns reference materials for use in geochemical trace analysis, ore grade assays and the analysis of concentrates for establishing the values of shipments. Suggestions are given for the sources and preparation of various types of reference materials that may need to be developed for in‐house