The current study deals with experimental use of an ultrasound generator for phacoemulsification and its effect on bovine corneal endothelium. The extent of the endothelial defect was defined by staining cell borders and nuclei. Histological examination showed that endothelial cells on the edge of a defect had no nuclei and were partially detached from the Descemet's membrane in some cases. Quantitative determinations of endothelial cell defects demonstrated the effects of distance from the generator (1, 2, and 3 mm) as well as duration of exposure. At 2 and 3 mm, addition of sodium hyaluronate (Healon) to the incubation medium was associated with a statistically significant reduction in size of the endothelial defect.