A 79-year-old man with marked hepatosplenomegaly and lymphadenopathy was admitted to the hospital. Analysis of serum protein resulted in the diagnosis of gamma-chain disease (total protein 6.2 g/dl, M-protein positive, IgG 4150 mg/dl, IgG-Fc fragment positive). Specimens obtained by lymph node biopsies showed infiltration of plasmacytoid cells, which were stained with anti-IgG but not with anti-kappa or anti-lambda antibodies. The patient was given combination chemotherapy, but without effect. Then a regimen of long-term administration of low-dose etoposide was begun, and resulted in remission of the lymphadenopathy, hepatosplenomegaly, and abnormal IgG.