We analyzed the data from seroepidemiologic survey of anti-HTLV-I serum antibody (HTLV-1 Ab) and 16 adult cases of T-cell leukemia (ATL) in China (1984-1994). The results showed that the positive rate of HTLV-I Ab of the population of China was 0.54%, the birth or residence places of HTLV-I carriers and all the patients with ATL were mainly distributed in the coastal provinces and the northeast China, and a small endemic area of HTLV-I and ATl was found in Fujian Province (HTLV-I Ab positive rate, 2.1%). The HTLV-I in China may be transmitted from Japan or originated from China. The clinical characteristics of the cases included onset in adulthood; frequent skin lesions, lymphadenopathy and hepatosplenomegaly; no mediastinal mass; the ATL cells from peripheral blood with polymorphism nuclei and mature T cell immunophenotype HTLV-IAb positive in most of the cases tested (5/8); mostly acute type; with a median survival period of 3.5 months.