The effects of several intraocular irrigating solutions on the corneal endothelium of rabbit and monkey corneas were evaluated, utilizing a specular microscope perfusion system with both scanning and transmission electron microscopy. Corneas perfused with 0.9% sterile isotonic physiological saline swell at a rate of 60mum to 90mum/hr; endothelial cells separate from each other and show extensive degenerative changes. Corneas perfused with lactated Ringer solution swell at a rate of 37mum to 40mum/hr, and the endothelial cells show slower, but progressive degeneration. Corneas perfused with balanced salt solution swell at 24mum to 31mum/hr, and degenerative changes become severe only after two hours. Corneas perfused with Ringer solution containing bicarbonate, reduced glutathione, and adenosine do not increase in thickness, and there is minimal deterioration of endothelial ultrastructure for periods of up to six hours.