The Human T-Cell Lymphotropic Virus Type I is known as the etiologic agent of Adult T-Cell Leukemia. The HTLV-I is also related to a chronic myelopathy, which includes (auto) immune-mediated inflammatory injury in its pathogenesis. Other autoimmune syndromes such as Rheumatoid Arthritis and Sjögren’s Syndrome are reported in infected patients. In those patients, these clinical conditions seem to be the result of the interaction between the virus as an environmental agent and host susceptibility, leading to an aberrant functioning of immunomodulatory mechanisms, cellular proliferation and inflammation. The study of clinical and immunological aspects of the HTLV-I-associated rheumatic manifestations may contribute to the better understanding of the auto-immune diseases.