The lower esophageal sphincter pressure has been measured intraoperatively in 200 patients with gastroesophageal reflux and in three patients with achalasia. Lower esophageal sphincter pressure is measured before and during repair. Calibrating the cardia during performance of the median arcuate posterior gastropexy allows a sphincter pressure between 50 and 57 mm. Hg to be obtained at operation. The postoperative pressures have ranged between 15 and 25 mm. Hg, or approximately half of the intraoperative pressure. No patient with a spincter pressure of 15 mm. Hg or greater has reflux according to postoperative pH and pressure studies. Correction of reflux correlates well with relief of symptoms. Three patients with achalasia had intraoperative manometrics during myotomy. The lower esophageal sphincter pressure was lowered and the length of the lower esophageal sphincter was shortened. Dysphagia was corrected without producing reflux. This is the first report of measurement of lower esophageal sphincter pressure in anesthetized patients. Intraoperative measurement of sphincter pressure is a safe, simple, and reliable technique which allows the surgeon, for the first time, to determine the status of the lower esophageal sphincter during the operation. This technique should be standard for all operations on the gastroesophageal junction.