In order to elucidate the pathological and epidemiological features of malignant lymphoma (ML), particularly of adult T-cell lymphoma/leukemia (ATLL) in the Kagoshima district, age-adjusted and age-specific incidence rates of malignant lymphomas were estimated on 3239 histologically confirmed cases between the years 1963 and 1987. There was a marked increase in the incidence rate from 1976 (4.9) to 1982 (8.5) due to the increase of T-cell lymphomas. The increase was not conspicuous after 1982. Immunohistochemically, all of the 429 MLs found in 1985 and 1986 were examined on paraffin sections and 70 ATLL cases on fresh frozen sections. T-cell ML comprised 65.3%, B-cell ML 30.5%, Hodgkin disease 2.6%, and histiocytic ML 1.2%. Most of ATLL cells were phenotypically CD4+ CD8-, 14% of ATLL cases showed CD4+ CD8+, 6% were CD4- CD8+, and 7% were CD4- CD8-. The simulataneous expression of IL 2 and IL 2R was seen in 8 (16%) out of 56 patients examined. Therefore, a proliferation by autocrine mechanism does not seem to be a major course of ATLL progression.