Fundoplication (Nissen operation) was employed in 27 patients with hypotension of the inferior esophageal sphincter. In 17 there was an esophageal hiatal hernia; in six patients gastroesophageal reflux followed operative or manipulative procedures on the esophagogastric junction. No anatomic abnormality was detected in three patients, and in one the sphincter had been rendered nonfunctional by slceroderma. Eighty-nine percent of the patients were improved by operation, the results being better in those without shortening of the esophagus or stricture formation or both. Only one patient complained of the "gas bloat" syndrome. Preoperative and postoperative esophageal manometry revealed statistically significant (P <.001) increases in amplitude (5.7 ± 1.1 to 16.3 ± 2.3 mm Hg) and length (2.7 ± 0.3 to 4.8 ± 0.2 cm) of the inferior esophageal sphincter.