Cellular and humoral immunity was studied in pigmented guinea pigs after one injection in the two hind footpads of extract of bovine retina or crude suspensions of rod outer segments (ROS) with complete Freund's adjuvant. In vitro macrophage migration inhibition experiments showed that the antigens which give rise to cellular immunity are mainly located in the pigment epithelium-photoreceptor layers and are devoid of species specificity. With the complement fixation method, the evolution of serum antibodies in anti-ROS guinea pigs was compared with clinical and histological data during the course of the ocular disease. Antibodies appeared in the 2nd week, slighly before the lesions, reaching their maximum level at the 4th week and decreased pari passu with the clinical ocular inflammation, while choroidal cellular infiltration and retinal alterations persisted for several months. Attempts to transfer the disease passively with concentrated serum from enucleated donors were successful. The immune sera were injected locally by different routes. Repeated subconjunctival injections - the less traumatic way - induced severe chorio-retinal lesions.