Since the discovery of numerous cases of recurrent bacterial infections resulting from agammaglobulinemia and lack of acquired serum antibodies in children and adults, there has been renewed interest in the general problem of resistance to infection. It has been shown recently that patients with multiple myeloma likewise are susceptible to recurrent bacterial infections, particularly pneumococcal pneumonia.1-5 Zinneman and Hall 2 and Lawson and his associates 4 demonstrated that certain patients with multiple myeloma and large amounts of abnormal serum globulins had little or no normal γglobulin or serum antibody. This fact seemed to account for their peculiar susceptibility to pneumococcal pneumonia. Experiences at the Minneapolis Veterans Administration Hospital with 51 cases of multiple myeloma in the period from 1947 to 1957 are reported in the light of recent knowledge of protein abnormalities and with special emphasis on the incidence of infection, particularly bacterial pneumonia. Materials and Methods In each