Seven isolates of human T cell leukemia virus type 1 (HTLV-1) were taken in southern India and phylogenetically analyzed to gain new insights into the origin and dissemination of HTLV-1 in the subcontinent. The new Indian HTLV-1s were found to be members of subgroup A (Transcontinental subgroup) of the Cosmopolitan group. They formed three different clusters (South African/Caribbean, Middle Eastern, and East Asian clusters). These results demonstrate that Indian HTLV-1s are genetically heterogeneous and include the most divergent strain of subgroup A. On the basis of these results, we speculate that subgroup A HTLV- 1s may have been present for thousands of years in India.