During the past year we have evaluated the identity and topographic localization of immunocompetent cells in patients with different stages of uveitis and in Lewis rats with experimental autoimmune uveitis by immunopathological study (immunoperoxidase technique). The data demonstrated that the predominant infiltrating cells in the eye was mainly T-lymphocytes with the T-helper/inducer cells in the early stage and a relative increase of T-suppressor/cytotoxic cells in the later stage. We have also observed the expession of class II antigens on some ocular tissue (vascular endothelium, retinal pigmented epithelium and fibroblast) prior to and during the development of the disease, and the consequence of inflammation: destruction of photoreceptors, formation of cyclitic or preretinal membrane and gliosis. These observations may reflect the kinetics and regulation of the ocular autoimmune process and help us to understand the pathogenesis of these ocular diseases.