One hundred and fifty-four patients with a monoclonal gammopathy, diagnosed between 1965-1974 in the Hadassah University Hospital are reviewed with special reference to the relative incidence of associated disorders. Most patients (63 per cent) had immunoproliferative disorders (multiple myeoloma, macroglobulinemia of Waldenstrom, chronic lymphocytic leukemia, and other non-Hodgkin lymphomata). A non-B-cell malignancy, either of blood-forming tissues or of epithelial origin, was found in 6.5 per cent. Miscellaneous nonmalignant diseases (chronic liver disease, diseases of known or suspected autoimmune origin, chronic infections, Gaucher's disease), which have been reported in the past in association with a monoclonal gammopathy, were diagnosed in 15 per cent of the patients in this series. Twelve per cent of the patients were either asymptomatic or had diseases not known to be associated with monoclonal gammopathies. Amyloidosis was diagnosed in 3.3 per cent of the patients.