B-cell neoplasms are not infrequently associated with autoimmune diseases. A 60-year-old man with multiple myeloma developing in an early stage primary biliary cirrhosis was reported. Initially, he had hypergammaglobulinemia with monoclonal gammopathy (IgG-kappa type), elevation of serum IgG and IgM, and positive serum antimitochondrial antibodies. There were compression fractures of the lumbar vertebrae, where bone marrow aspiration revealed proliferating myeloma cells. Liver biopsy revealed destruction of bile duct surrounded by an inflammatory infiltrate, which was consistent with stage I primary biliary cirrhosis. The association suggested the role of immunoregulatory abnormalities in the development of multiple myeloma.