Ocular manifestations in patients infected with human T-lymphotropic retrovirus type I (HTLV-I) consisted of a wide range of neoplastic, infectious and noninfectious vascular or inflammatory lesions. These disorders were associated with two distinct HTLV-I-induced systemic diseases, ie, adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy. Five of the 10 cases of adult T-cell leukemia/lymphoma had inflammatory or opportunistic infectious ocular lesions, including cytomegalovirus retinitis or eyelid tumor as part of generalized lymphomas. Four of the 17 cases of HTLV-I-associated myelopathy showed noninfectious lesions such as isolated, transient cotton-wool spots and granulomatous iridocylitis. Twenty-four (26.9%) of 89 cases with various ocular diseases but no HTLV-I-induced systemic disease had antibodies to HTLV-I in the serum. The aqueous humor antibodies to HTLV-I in the seropositive carriers were negative, except one carrier case who showed isolated cotton-wool spots in one eye and massive vitreous opacities in the other eye.