The survival time of rabbit corneal endothelial cells in isolated perfused cornea is extended dramatically by the addition of oxygen free radical scavengers. Lipid soluble antioxidants were found to be more effective than water soluble non-enzymatic antioxidants in extending the survival time. The ultrastructural appearance of endothelial cells treated with vitamin E was compared with controls. Vitamin E treated endothelial cells retained normal appearance up to 12h, but without vitamin E, breakdown of the endothelial cells occurred after 6h of perfusion. In these cells the major sites of damage were the mitochondria and the endoplasmic reticulum, whereas the plasma and nuclear membranes appeared normal.