The effects of perfluoropropane gas on the cornea were compared with those of sulfur hexafluoride gas following injection into the anterior chamber of rabbits and cats. Injection of 0.15 mL of gas produced a perfluoropropane bubble that lasted 22 days compared with a sulfur hexafluoride bubble that lasted seven days. The sulfur hexafluoride bubble produced corneal edema for as long as the gas was present. With perfluoropropane, corneal edema persisted even after the gas bubble disappeared. In another group of cats, multiple sequential injections of sulfur hexafluoride to maintain a gas bubble of duration comparable with the perfluoropropane bubble also produced edema as long as gas was present. Clinical corneal edema, endothelial fibrin deposition, endothelial opacities, and retrocorneal membrane were observed by slit-lamp and light, scanning, and transmission electron microscopic examinations of the corneas exposed to perfluoropropane but not of those exposed to sulfur hexafluoride. Prolonged corneal endothelial contact by perfluoropropane results in corneal edema due to endothelial dysfunction, which persists in cats probably because feline endothelium is less capable of regeneration than that of rabbit.