An 88-year-old woman was admitted with generalized lymphadenopathy, anemia, and thrombocytopenia. On admission, a peripheral blood examination showed a red blood cell count of 146 x 10(6)/microliter, a hemoglobin concentration of 6.9 g/dl, and a platelet count of 5.0 x 10(4)/microliter. Blood examination detected polyclonal hypergammaglobulinemia; the results of the direct/indirect Coombs' test were positive; and an elevated cold agglutinin titer and high platelet associated IgG (PA-IgG) level indicated the existence of autoantibodies. Serum cytokine measurements disclosed an elevated level of interleukin-6 (IL-6). Immunoblastic lymphadenopathy-like T cell lymphoma was diagnosed on the basis of lymph node biopsy specimens. VP-16 and steroid therapy alleviated the patient's lymphadenopathy, anemia, thrombocytopenia, and hypergammaglobulinemia. These findings suggest that tumor cells with a T cell phenotype produced IL-6 in large quantities, thus provoking B-cell and plasmacytic histologic changes and humoral disease manifestations, including hypergammaglobulinemia.