We performed 26 consecutive intracapsular cataract extractions with lens implantation. The last 17 implantations were performed with air instilled in the anterior chamber, whereas the first nine operations were performed without air. The central corneal endothelium of each eye operated on was photographed before and within five days after lens implantation. A computer analysis of the endothelial photographs showed that, on the average, 32% of the central corneal endothelial cells were lost during lens implantation without the use of air and 15% were lost when the lens was implanted with air. Increased endothelial cell loss was significantly correlated with the failure to implant the lens with use of air, with increased operative endothelial trauma, and with higher postoperative intraocular pressures. A significantly larger increase in corneal thickness on the first postoperative day occurred in patients with larger or more varied cell sizes preoperatively.