The endothelium of 40 eyes from 38 diabetics were examined before and after argon photocoagulation. Twenty-two eyes were reexamined six weeks postoperatively. Changes in endothelial cell density were compared with regard to the energy delivered to the eye. There was no statistically significant change in the endothelial cell density in the immediate postoperative period. A statistically significant but small change in endothelial cell density was found in the six-week follow-up group when cell density was compared with energy delivered to the eye by the argon laser photocoagulator. Implications and possible causes for these observations are discussed.