Immune intraocular inflammation was induced in primates with homologous retinal outer segments. Perivascular retinitis, uveitis, and edema of the optic nerve head were the prominent acute clinical features. Acute and chronic inflammation was seen in the central and peripheral retinal vessels and granulomatous infiltration was present in the choroid of the uvea. Selective degeneration of the outer segments of the photoreceptor cells of the retina with sparing of the inner segments and of the adjacent pigment epithelium was confirmed by light and electron microscopy. This study strongly suggests that photoreceptor outer segments are highly and specifically immunogenic. The inciting antigen has yet to be identified. Implication of rhodopsin will have to await further studies since it exists as the essential protein in the outer segment.