25 patients were operated with Heller's procedure for achalasia of the esophagus. A study of their clinical, radiological, manopetric and pH-metric evolution was carried out over an average period of 75 months. While the long-term results were satisfactory in 80 % of these patients, the poor results were essentially caused by the occurrence of gastroesophageal reflux. An objective study performed by manometry and pH-metry allowed evidencing true asymptomatic acid reflux. It is necessary to devise an anti-reflux valve if the myotomy reaches as far as the cardia.