The development of a population-based registry on paraproteinemia and multiple myeloma is described. A unique feature of this registry is the multidisciplinary approach to obtain and collect new cases. Clinical chemists, internists, hematologists, and pathologists could all enter patients. All patients newly diagnosed in the mid-western part of The Netherlands (1.7 million inhabitants in 1992) with a paraproteinemia or multiple myeloma in 1991, 1992, and 1993 were included. The project was composed of a registry of clinical and laboratory data extracted from the patient's records, storage of 1 ml serum at diagnosis, and a yearly follow-up. A total of 1832 entries was received, of which 83% met the inclusion criteria. Comparison of this database with the Regional Cancer Registry showed that the paraprotein registry was successful as far as registration of myeloma patients was concerned. We conclude that the multidisciplinary approach used in this paraprotein registry is feasible and has resulted in a unique collection of patients for studying potential pre-malignant conditions such as paraproteinemia.