Thrombomodulin (TM) is a protein, present on intact endothelial cell surfaces, that plays a major role in the protein C anticoagulant system. Plasma TM is produced by injured endothelium, and is recognized in circulating blood or urine as a sign of endothelium cell damage. The localization of TM within the eye and its kinetics in the eye and the serum were investigated in rats with experimental autoimmune uveoretinitis (EAU). An immuno-histochemical study showed the presence of TM at sites of fibrin in the anterior chamber and retinal vasculitis. The amount of TM in the eye increased with progression of intraocular inflammation, but the serum level of TM did not significantly differ from the values in the control group. These data suggest that TM may play a role in preventing thrombosis in cases of vasculitis and fibrin formation in the anterior chamber in EAU, thus maintaining blood flow and the fluidity of aqueous humor.