Chromosomal abnormalities in Castleman's disease with high levels of serum IL-6 were reported. A 69-year-old male was found to have superficial lymph node swelling and polyclonal hypergammaglobulinemia, when he was admitted to the department of otolaryngology for carcinoma of the tongue in July 1991. In December, he was referred to our department after completing radiation therapy. Laboratory examination revealed 7.7 g/dl hemoglobin, 10.8 g/dl total protein, and 56.0% gamma-globulin. Serum electrophoresis revealed polyclonal hypergammaglobulinemia and no Bence-Jones protein. Bone marrow aspirates showed an increase of plasma cells to 21.8%. Serum IL-6 was 252 pg/ml. Chromosomal analysis of cells in the lymph node showed a karyotype of 46,XY,t(7;14)(p22;q22). The lymph node histology showed marked hyperplasia of plasma cells at interfollicular areas. These plasma cells were stained with both anti-kappa and anti-lambda antibody. He was diagnosed as multicentric form Castleman's disease. Treatment with prednisolone and melphalan resulted in improvement of clinical findings such as anemia, lymph node swelling and hypergammaglobulinemia in concurrence with decrease in serum levels of IL-6. Since the IL-6 gene is located on 7p21-22, the translocation 7; 14 may be related to the high level of serum IL-6.