O-49 Viro-epidemiological findings of HTLV-I subtypes suggest that HTLV-I carriers in southern Japanese and South American Andes natives are ethnically related. In order to clarify the ethnic relationship between southern Japanese and Andes natives, we analysed HLA class I and class II alleles and haplotypes of asymptomatic HTLV-I carriers (AC), ATL and HAM/TSP from southern Japanese (Kagoshima), Nivkhi (Sakhalin) and Andes natives of Colombia. Chile and Bolivia. Southern Japanese AC, ATL and HAM/TSP were characterized by three groups of HLA alleles, group I (A*26, B*4002, B*4006, B*48, DRB1*0901, *0403, *1402, *1406, *0802), group II (A*24, B*07, B*35 B*52, DRB1*0101, *1502, *0405, *0803) and group III (A*02, A*11, A*31, A*33. B*39, B*44, B*48, B*4001, B*15, B*55, DRB1*0404, *1501, *1101, *1302, *1401, *1403, *1405). Group I was associated with ATL, group II with HAM/TSP and group III with AC and general population of Kagoshima. The Nivkhi were found HTLV-I positive and their HLA alleles were related to those of Kagoshima and Okinawa natives. HTLV-I carriers of Andes natives in Colombia, Chile and Bolivia posessed HLA-A*02, A*24, A*28, A*31, B*07, B*15, B*35, B*39, B*4002/6, B*44,B*48,B*51,DRB1*0101, *0403, *0404, *0901. *1101, *1402, *1406 and *1602 comprising the unique haplotypes of B*4002/6-DRB1* 0901/0802, B*35-DRB1*0403, B*55-DRB1*1101, B*48-DRB1*1402 and B*39-DRB1*1406 which were found among southern Japanese AC. ATL and HAM/TSP. These results indicate that subpopulations of Japanese and Andes natives are ethnically related and come from the same cradle of mongoloid HTLV-I carrier's lineage (the transcontinental subgroup A).