The endothelium of 36 clear penetrating keratoplasties, performed 1 to 19 years previously, was examined and photographed with the clinical specular microscope. There were fewer central endothelial cells in the transplants than in normal corneas. There was no significant correlation between graft endothelial cell density and corneal thickness, rejection episodes, the disease necessitating kertoplasty, or the method of donor tissue preservation. Corneas transplanted from younger donors to younger recipients had significantly more central endothelial cells. Transplanted corneas appeared to lose endothelial cells over a period of time, just as normal corneas do.