Although antigens of the human major histocompatibility complex, HLA, appear to be involved in the rejection of corneal allografts, the expression of these antigens by cells of the human cornea remains controversial. Using sensitive immunoperoxidase techniques, we readily demonstrated class I HLA antigens on corneal epithelial, stromal, and endothelial cells, regardless of donor age. Moreover, the expression of class I antigens by epithelium increased markedly from the central to the peripheral cornea. Finally, class II HLA antigens were found on cells scattered throughout both central and peripheral epithelium as well as the stroma. A cornea obtained from a donor of known HLA type expressed all expected and no unexpected polymorphic HLA determinants in the cornea, in a pattern similar to that seen for monomorphic HLA determinants.