Peroral endoscopic myotomy is an accepted treatment of achalasia. Some of the treatment failures can be attributable to an insufficient length of the myotomy on the gastric side, because of a more technically challenging submucosal dissection. We assessed the feasibility and the impact of an intraoperative esophageal manometry during the peroral endoscopic myotomy procedure. A high-resolution manometry catheter was introduced through the nostril before the endoscope, and left in place during the peroral endoscopic myotomy procedure. The lower esophageal sphincter pressure was recorded throughout the peroral endoscopic myotomy. The myotomy was extended on the gastric side until the lower esophageal sphincter pressure dropped below 10 mmHg. We included 10 patients (mean age = 55 years old, 3 men) treated by peroral endoscopic myotomy for type I (3/10), type II (3/10), type III achalasia (3/10) or esophagogastric junction outflow obstruction (1/10). Manometric recording was possible in all patients. The median (IQR) lower esophageal sphincter resting pressure was 23 (17-37) mmHg before myotomy, 15 (13-19) mmHg at the end of the tunnel, and 7 (6-11) mmHg at the end of the myotomy. In 4 patients out of 10, the myotomy was extended on the base of the intraoperative manometry findings. High-resolution esophageal manometry is feasible during the peroral endoscopic myotomy procedure, and leads to increase the length of the gastric myotomy in 4 out of 10 patients. However, the cumbersome nature of intraoperative high-resolution manometry during peroral endoscopic myotomy and the high frequency of gastro-esophageal reflux disease after extended gastric myotomy suggest to limit this technique to selected patients refractory to a first myotomy.