The various traumatic lesions occurring in the corneal endothelium during phacoemulsification were studied in the eyes of anesthetized rabbits. A comparison was made between the effects of massive perfusion of the anterior chamber with simple isotonic saline or Earle's solution, ultrasound emission, total phacoemulsification, and classical extracapsular extraction. The endothelium was examined by electronic scanning microscopy to cover large areas of the endothelium. Simple perfusion with Earle's solution does not alter the appearance of the endothelium, though some modifications in apical digitations may be observed. Perfusion with isotonic saline solution for 15 minutes modifies the appearance of the endothelial surface, with early necrosis in several cells. Ultrasounds provoke complete necrosis of a few isolated cells but do not cause major changes in most of them. Phacoemulsification produces endothelial ulcerations, probably from the trauma from lens debris. Extracapsular extraction, difficult in the rabbit, is the cause of much larger lesions with cell necrosis and vast areas of ulceration.