To elucidate the role of macrophage migration inhibitory factor (MIF) in ocular inflammation, we examined the localization of MIF in the normal anterior uveal tract of rats. Immunohistochemistry using an anti-MIF antibody revealed that MIF was present in non-pigment epithelial cells of the ciliary body and the epithelial cells of the iris. Western blot analysis of these tissues showed a single band specific for MIF protein. The expression of MIF mRNA in these tissues was further confirmed by reverse transcription-polymerase chain reaction. Since MIF is known to be a potent proinflammatory cytokine, identification of the protein in iris and ciliary epithelial cells suggests the possibility that it may play an important role in ocular inflammation.