The aqueous humor of 14 patients with brucellar uveitis was studied with microscopic methods to show the local production of antibodies specific for Brucella. In four of ten cases with active uveitis, we demonstrated specific antibodies by computing the relative immunoglobulin concentration ratio (C value); the remaining six cases were not tested for IgG. No antibodies were detected in the aqueous humor in three inactive cases and in one case of posterior active uveitis. Levels of immune complexes were elevated in the aqueous humor in 18 cases of brucellar and non-brucellar uveitis, with average values of 110 ng/ml. These immune complexes were specific to brucellar antigens in three of four cases of brucellar uveitis and were not detected in six cases of non-brucellar uveitis. The demonstration of plasmocytes and Russell bodies in the uveas of these patients provides a cellular basis for the local production of immune complexes and immunoglobulins. The unusual isolation of Brucella melitensis in subretinal liquid from one of our cases suggests that infectious uveitis in the actual presence of the organism germ could be an infrequent event. It is probable that the presence of antigenic brucellar fragments within the local immune reaction could be the main pathogenic event causing the ocular damage of brucellar uveitis.