The connective tissue cells in a large central area of the cornea were killed by freezing without apparent permanent damage to the optical properties of the cornea. The dead cells were replaced by mitosis and migration of the keratoblasts surrounding the injury. Injected H3 thymidine was incorporated in the regenerating cells. The cells concerned with thymidine uptake were found in a ring shaped band immediately adjacent to and surrounding the injury. Cells further removed from the injury in the corneal periphery did not participate in this process. Most DNA synthesis, as shown by tritiated thymidine uptake, occurred during the first few days but some DNA synthesis was demonstrable as late as 7 to 9 days after injury. When the depopulated zone decreased in diameter, as new cells moved inward, the ring of regenerating (DNA synthesizing) cells became smaller. After new cells formed in the regeneration zone they migrated into the depopulated area within a few days. The central cornea, after a few weeks, became filled with cells normal in number and appearance of which about 25% were demonstrably radioactive. The tritiated thymidine label, although diluted by cell division which occurred early in the regeneration process, persisted in these cells indefinitely. Such corneas appear to be ideal material for transplantation experiments in which the persistence of donor cells could be studied. This has been accomplished in a series of preliminary experiments in which the indefinite persistence of the donor cells in corneal grafts was demonstrated.