To summarize, we found that high levels of MIF were detected in the serum of uveitis patients with Behçet's disease, VKH disease, and sarcoidosis, as well as idiopathic iridocyclitis. In Behçet's disease and sarcoidosis, the MIF levels were higher in the active uveitis stage than in the inactive stage. Serum MIF increased after corticosteroid therapy in VKH disease. A high aqueous humor MIF concentration was detected at the onset of EAU. Finally, anti-MIF antibody suppressed EAU when administered in the early phase. MIF is thought to be an important cytokine in the pathogenesis of uveitis.