The effects of pneumoperitoneum on the lower esophageal sphincter (LES) were evaluated during laparoscopic operation for esophageal achalasia. Intraoperative manometry was performed in three patients who underwent laparoscopic cardiomyectomy with Dor's fundoplication and five patients who underwent laparoscopic cholecystectomy (LC). The LES pressure and the length of the high-pressure zone (HPZ) did not change during pneumoperitoneum in either the achalasia and the LC group. In the achalasia group the LES pressure was sufficiently decreased following completion of cardiomyectomy, and the length of the HPZ was found to be sufficiently long after completion of fundoplication. The postoperative courses of the achalasia patients were uneventful, and they have had no symptoms of achalasia or gastroesophageal reflux since the operation. Accordingly, intraoperative manometry during 12 mmHg pneumoperitoneum was considered to be available for laparoscopic surgery for esophageal achalasia.