Despite an estimated 1 million case of human T-lymphotropic virus type I (HTLV-I) infection worldwide, and over 197,000 cases of infection with HTLV-II in the United States, the clinical outcomes and pathogenesis of HTLV-I and -II infection are still not well defined. Data from the previous funding period of this HTLV Outcomes Study (HOST) indicate that HTLV-II predisposes to pneumonia, bronchitis and arthritis, causes a myelopathy similar to HTLV-I associated myelopathy (HAM), and is associated with increased all-cause mortality. HTLV-I has previously been associated with adult T-cell leukemia (ATL), HAM and arthritis, uveitis and iritis. These pulmonary, neurologic and immunologic syndromes have not been well characterized clinically or biologically, especially for HTLV-II. This Competing Continuation Project will test the following hypotheses: 1. Infection with HTLV-II, and to a lesser degree HTLV-I, predisposes to pneumonia and bronchitis because of HTLV-induced, immune-mediated pulmonary damage. 2. HTLV-II causes myelopathy resembling HTLV-I associated myelopathy (HAM) via similar mechanisms immune-mediated neurotoxicity. 3. HTLV-II, and perhaps HTLV-I, is associated with increased mortality, perhaps due to a higher death rate from malignant and/or cardiovascular causes. 4. HTLV-I and -II are associated with a higher incidence of arthritis and other autoimmune conditions. We shall test these hypotheses during additional prospective investigation of the HOST cohort of 154 HTLVI, 387 HTLV-II and 799 stratum matched seronegative former blood donors enrolled in 1990-92. 6 biennial visits of this cohort have been completed to date. This application proposes 2 additional visits from 2005 through 2009, including structured health interviews, screening physical examinations, medical record review and targeted physician diagnostic work-ups. Blood will be collected from all subjects, and bronchoalveolar lavage fluid and cerebrospinal fluid from subsets with disease, for studies of HTLV virology and immunology.