The ability of retina derived antigens to induce a strong immunological response resulting in immunopathological alterations in the retinae of experimentally immunised animals has been well established (reviewed by Faure, 1980). The photoreceptor specific soluble protein, known as S-antigen, has been implicated as one of the most uveitopathogenic components of the retina (Wacker et al. , 1977). There is a growing number of reports suggesting immunological alterations in human retinal degeneration, such as retinitis pigmentosa (RP), and chorioretinal inflammatory diseases, either involving specific retinal autoimmunity or an imbalance in immunological control mechanisms (reviewed by Forrester et al. , 1986). This thesis has sought to further characterise S-antigen, and to examine the specificity of autoimmunity in the RCS rat retinal dystrophic model, human uveitis, and RP.