Ocular specimens and sera from 12 patients with onchocerciasis and 10 controls were studied. A mild to moderate chronic inflammatory cellular infiltration was present in the conjunctiva of the onchocerciasis patients. T-lymphocytes were the predominant inflammatory cells, with the T-suppressor subset being significantly increased in the onchocerciasis patients, compared to controls. In the onchocerciasis patients, such nonlymphoid cells in the conjunctive and iris as vascular endothelia, pericytes, and fibroblasts showed an increase in expression of class II antigens. The anti-Onchocerca volvulus antibodies in the sera and aqueous humor were significantly higher in the patients compared to the controls. These findings suggest that T-cells are important in the ocular immune response to Onchocerca and that expression of class II antigens on nonlymphoid cells and the humoral factors may play a critical role in the ocular onchocerciasis. Retinal autoantibodies found in sera of these 12 patients were bound to the inner retinal layer and photoreceptors. Such autoimmune antibodies may play a role in the pathogenesis of the retinal degeneration and optic atrophy that occurs as a consequence of onchocerciasis.