The acute and lymphoma types of adult T-cell leukemia/lymphoma (ATL) usually have a very poor prognosis, although some patients achieve long survival after chemotherapy. A total of 114 patients with these aggressive types of ATL were newly diagnosed at our institution from 1975 to 1989. By multivariate analysis, poor performance status and high serum creatine levels were associated with shortened survival. With combination chemotherapy, 20 patients achieved complete remission (CR), 53 achieved partial remission (PR) and 35 showed no response. Fifteen of the CR or PR patients survived for more than two years and all other patients survived for less than two years. As compared with short survivors (< 2 years) after remission, long survivors (> or = 2 years) after remission had a higher CR/PR ratio, a longer time until remission and a higher doxorubicin dose to achieve remission. Death due to causes other than the primary disease occurred in 18% of short survivors after remission and in 11.2% of nonresponders, but in none of the long survivors. Long survivors with acute ATL included 6 patients with CR and 5 patients with PR. All four lymphoma type ATL long survivors achieved CR. Monoclonal integration of HTLV-I provirus was detected in the peripheral blood mononuclear cells of all 3 PR long survivors with acute ATL studied, but was not detected in all 4 CR cases studied at remission. The minimum CD4/CD8 ratio of peripheral mononuclear cells at remission was < 1.0 in all acute ATL long survivors with CR, and was > 1.0 in all acute ATL long survivors with PR. Three out of six acute ATL long survivors with CR developed suspected viral infection just before achieving CR. Our findings show that in aggressive ATL the characteristics of remission are heterogeneous even among long survivors.