We investigated the effects of the iron chelator desferrioxamine (DFX) on thrombus formation in the arterioles and venules of the rabbit ear chamber. Thrombi were induced by irradiation with filtered light in combination with a fluorescent dye. The occlusive thrombus formation time was significantly extended by DFX. The mor-phological composition of thrombi in the arterioles and venules was different. In the arterioles, the thrombi consisted of platelet aggregation, but in the venules, platelets and leukocytes accumulated on the endothelium. This suggests that hydroxyl radicals may be important mediators in this model, as DFX is known as a hydroxyl radical scav-enger. Furthermore, the components of thrombi in the arterioles and venules in the skin microvascular system may be different