S-antigen, an organ-specific substance isolated from the retinal photoreceptor region, was shown to be a potent agent for the induction of experimental autoimmune uveitis. S-antigen and other ocular antigens were tested for their ability to induce blast transformation of lymphocytes from patients with a variety of ocular inflammatory diseases. Lymphocytes from 22% of patients tested manifested a positive memory response to the S-antigen prepared from bovine eyes. Responses to human S-antigen paralleled those found with the bovine. All of those with a positive response had active or inactive retinal lesions. Some posterior uveitis patients responded to crude retinal extracts but not to S-antigen, indicating the possible role of other retinal antigens still to be purified. Control subjects did not manifest a positive immune response to the S-antigen, nor did patients with anterior uveitis. Possibly, these responses play some role in the pathogenesis of the disease.