A review of 100 patients with HTLV-I associated myelopathy revealed 9 cases of retinochoroidal degeneration. The ocular disease was characterized by late onset, usually bilateral, progressive degenerative changes of the retina and choroid, which were preceded by, concurrent with, or followed by HTLV-I associated myelopathy. Ophthalmoscopic features were consistent with diffuse or localized retinochoroidal degeneration, the resultant functional disturbance being dependent on the extent of disease. It is noteworthy that the clinical picture in 3 cases was indistinguishable from primary retinitis pigmentosa. However, based on the prevalence of primary retinitis pigmentosa in the general population estimated from a questionnaire to ophthalmologists in the area, it was plausible that retinitis pigmentosa in HTLV-I associated myelopathy does not represent a coincidence of primary retinitis pigmentosa but a meaningful association with the neurological disease. Hence, we propose the existence of HTLV-I associated retinochoroidal degeneration (HARD) as a distinct disease. An additional study revealed that 21 (17.8%) of 118 patients with isolated, retinitis pigmentosa were seropositive for HTLV-I, the ratio being not significantly different from that in the general population. Therefore, the hypothesis that HTLV-I also contributes to an isolated form of retinochoroidal degenerative disease is not readily acceptable.