On March 27, 1990, the National Cancer Institute sponsored a workshop on the epidemiology of multiple myeloma, held at the National Institutes of Health. This book comprises articles prepared by participants in this work shop. Discussed in these papers are: the descriptive and analytic epidemi ology, differences in risk factors between blacks and whites, monoclonal gammopathies and their progression, and hypotheses regarding the etiology and pathogenesis of multiple myeloma. Several epidemiologic research areas received particular attention during this workshop, and are reviewed in detail in this volume. There have been striking increases in the incidence of multiple myeloma over the past thirty years, especially among older individuals and blacks, which may not be entirely explained by changes in diagnostic capabilities. Occupational and environmental exposures have been associated with an increased risk of multiple myeloma, including farming exposures, occupational exposure to petroleum and rubber processing, exposure to ionizing radiation, and asso ciations with persistent virus infections. The most striking epidemiological finding is reflected in the differences in incidence rates of multiple myeloma which are twice as high in blacks as compared with whites. Further, since 1950 the mortality rates for multiple myeloma have quadrupled in blacks while doubling for whites. Among hematopoietic malignancies, multiple myeloma is the only one with increased incidence and mortality rates among blacks. 1\vo major possibilities for explaining ethnic/racial differences in suscepti bility to multiple myeloma are genetic and environmental factors.