The clinical and pathological features of T-cell type malignant lymphoma related to human T-cell leukemia virus (HTLV) were investigated in eight patients presenting lymphadenopathy. Biopsy of lymph nodes showed an histology of diffuse non-Hodgkin's lymphoma. All patients were positive for anti-ATLA antibody and HTLV proviral DNA in the lymph node cells. Most patients showed pronounced hypercalcemia and high serum levels of lactic dehydrogenase. All patients died between 3 and 17 months (mean 8 months) after the onset of disease. HTLV-related malignant lymphoma should be added to the spectrum of ATL, being classified as a lymphoma type ATL.