Seroepidemiological, clinical and virological studies were carried out in an HTLV‐I endemic area to find out if HTLV‐I caused an intraocular inflammatory disorder, uveitis. The seroprevalence in patients with uveitis without defined etiologies (62/175, 35.4%) was significantly higher than that in patients with non‐uveitic ocular diseases (42/261, 16.1%) or in patients with uveitis with defined etiologies (8/78, 10.3%). Moreover, the seroprevalence in young adults (20–49 years) with uveitis without defined etiologies was 30/67 (44.8%), whereas it was only 10/107 (9.3%) in the other two groups. The uveitis in HTLV‐I carriers was characterized clinically by a moderate inflammation of the vitreous body accompanied by a mild iritis and retinal vasculitis. The proviral DNA of HTLV‐I was detected by polymerase chain reaction from the inflammatory cells in the anterior chamber in 9 out of 9 seropositive patients with the uveitis, but not in any of the tested patients with other types of uveitis. These data, thus, indicate that HTLV‐I causes a specific type of intraocular inflammation, uveitis.