The interaction of confronting corneal epithelium and endothelium has been studied by cultivation of corneas with open perforating wounds. In some experiments, the epithelium and the endothelium were initially damaged adjacent to the perforation, and the repair capacity was reduced by adding steroids or colchicine to the culture medium. The specimens were examined by scanning electron microscopy. The epithelium covered the stromal walls of the open perforation within 3 days. In most experiments, the epithelium and the endothelium met at the cut edge of Descemet's membrane, and this appeared to be a stable situation. However, if the endothelium was damaged and had reduced repair capacity, the epithelium invaded Descemet's membrane. The clinical implication is that the risk of epithelial ingrowth is present in eyes with a pathological endothelium.