A 4 mm circular defect was made on the endothelium by transcorneal freezing of 5 normal human corneas. The eyes were enucleated because of malignant tumours, patient age 3 to 74 years. After excision, the corneas were kept in culture medium for 3 (4) days, and subsequently prepared for SEM. At this stage, the defect was covered with endothelium, whose origin was a narrow zone adjoining the edge of the defect. The endothelium on the peripheral, undamaged part of the cornea did not seem to take part in the repair process, neither by proliferation, enlargement nor by migration. Dividing cells were found scattered on the damaged area. The repair process was found to be similar in all five eyes, irrespective of the age of the patient. In organ culture, the healing of corneal endothelial defects is similar in rabbits and in humans.