Human T-cell lymphotropic virus type I has been associated with a wide range of ocular conditions, including neoplastic, infectious, and inflammatory lesions. We studied a patient infected with human T-cell lymphotrophic virus type I who presented with deep retinal and subretinal infiltrates but without cells in the vitreous. The differential diagnosis included intraocular lymphoma and fungus infection. A chorioretinal biopsy specimen obtained for tissue diagnosis disclosed large atypical mononuclear cells located primarily at the level of the retinal pigment epithelium but focally involving overlying retina. Electron microscopy of this infiltrate showed features consistent with adult T-cell lymphoma/leukemia. Infection by human T-cell lymphotropic virus type I was verified by polymerase chain reaction studies conducted on peripheral-blood mononuclear cells. This case emphasizes the occurrence of intraocular lesions in adult T-cell lymphoma/leukemia that clinically show some features similar to those of the usual ocular lymphoma (reticulum cell sarcoma); diagnosis can be established by chorioretinal biopsy, thereby allowing appropriate therapy.