The antigenic composition of the human corneal endothelium, a cellular layer essential for maintaining corneal function, has not been well characterized. A novel corneal endothelial antigen was identified by generating a monoclonal antibody (MAb) against normal human corneal endothelial cells. This MAb, designated 2B4.14.1, reacted strongly by immunoperoxidase staining with the endothelium of corneas from all human donors tested but not with other corneal components, including epithelium and stroma. Positive immunohistologic reactions of 2B4.14.1 with several other human tissues, including kidney (parietal epithelium of Bowman's capsule, proximal convoluted tubule, ascending limb of Henle's loop, and distal convoluted tubule), glandular epithelia of numerous organs, and mesothelial linings of several thoracic and abdominal viscera, also were observed. One of the renal antigens recognized by 2B4.14.1 was identified as Tamm-Horsfall glycoprotein (THGP), based on the ability of the antibody to recognize THGP in western immunoblots and the abrogation of immunohistologic reactivity of the antibody by preincubation with purified THGP. These findings raise the possibility that the human cornea expresses a molecule with homeostatic properties similar to those ascribed to THGP. However, it is unlikely that the corneal antigen recognized by 2B4.14.1 is conventional THGP; a MAb specific for THGP did not react with corneal endothelium.