Electronic applanation tonometry appears to be the best, and is often the only, method for measuring intraocular pressure during the postoperative period following keratoplasty. This method was used to follow pressure changes after penetrating keratoplasty in 50 patients. The phakic patients generally showed little change in pressure. On the average, they attained a maximum pressure during the first postoperative week of 24 mm Hg. The aphakic patients and those undergoing combined lens extraction and penetrating keratoplasty, however, typically exhibited moderate to severe elevations in tension during the first few postoperative days. They attained average maximum pressures of 40 to 50 mm Hg. The clinical implications of these great pressure elevations are discussed, and the value of pressure measurements in guiding postoperative therapy is illustrated. © 1969.