A new international reference preparation for proteins in human serum has been recently proposed in Europe from the Community Bureau of Reference (Brussels) under the name CRM 470 (Certified Reference Material) and in the United States from the College of American Pathologists under the name RPPHS (Reference Preparation for Proteins in Human Serum).This serum based material offers the opportunity to the laboratories to standardize their serum protein concentrations, and to improve dramatically the transferability of the results from studies to the local working conditions. The International Federation of Clinical Chemistry strongly recommends the use of this preparation by all laboratories. The Belgian Institute of Hygiene and Epidemiology expects an improvement in the agreement of the results of the three proteins (IgA, IgG, CRP) included in its external quality control of the clinical laboratories. These proteins were omitted from the controls of the second semester of 1994, but would reappear in early 1995, after the conversion of the laboratories to the new protein calibrators. Of course, this implies the assigment of new reference ranges for most of the serum proteins, some of them being significantly modified (a 1-antitrypsin, haptoglobin, transferrin, C3, IgM). The clinical chemists must inform the physicians of these changes.