Experimental autoimmune uveoretinitis was induced in rats after one injection of purified retinal S antigen mixed with adjuvants. Lewis and PVG/c rat strains were highly sensitive. S antigens isolated from bovine, human, swine and guinea pig retinas had a high pathogenicity in Lewis rats, whereas allogenic S antigen did not induce the disease. Mycobacterial adjuvant was effect in both disease and antibody production but H. pertussis adjuvant strongly increased the severity of the ocular reaction, giving a hyperacute Arthus-type inflammation, even with low doses of antigen. No disease was found after immunization without bacteria (incomplete Freund's adjuvant or alum). With any bacterial adjuvant, the histological pattern was in agreement with the hypothesis of early reagin-mediated phenomena acting on the blood-retinal barrier, as suggested by previous experiments.