Anti-inflammatory potentials of a safe, common dietary component, quercetin, were investigated in suppression of intraocular inflammation induced by retinal S antigen. Lewis rats sensitized to S antigen were treated daily with intraperitoneal injections of quercetin. Control rats with S-antigen-induced uveitis were similarly treated with diluent. When compared with controls the treated group showed marked reduction in uveal and retinal inflammation and in vasculitis and perivasculitis. Morphometric analysis revealed a significant reduction (p < 0.005) in choroidal thickness when compared with that of control animals. These results clearly show the antiphlogistic effects of quercetin in experimental uveitis.