We used the clinical specular microscope to examine the endothelium of 14 clear penetrating corneal grafts that ranged from 4 days to 2 1/2 years posttransplantation. All the donor corneas had been preserved in organ culture at 37 C for up to five weeks before grafting. Ten of the transplants were aphakic. The graft endothelial cell density, although less than that of normal corneas of the same age, was similar to that of other transplants done by the same two surgeons using alternate methods of donor preservation. We found a significant inverse correlation between graft endothelial cell density and the age of the corneal donor.