The expression of MHC Class I and Class II antigens was investigated in the human uvea using monoclonal antibodies in an indirect immuno fluorescence technique. The anterior border layer of the iris, the non-pigmented and pigmen ted epithelium of the ciliary body, the external basement membrane of the ciliary body and the vascular endothelium in the uvea showed a positive staining for Class I antigens. The endothelium lining the bloodvessels in the uvea expressed the highest density of Class I antigens. Class II antigens were found only on single cells spread throughout the entire uvea. These cells did not seem to relate to any anatomical entity. No staining for Class II antigens was detected in the uveal blood vessel endothelium. The expression of HLA-antigens in the uvea may provide insight in the pathogenesis of certain HLA associated uveitis entities.