Intra-operative esophageal electromanometry (IEM), a method foretold by the authors since 1972, is indicated in the course interventions for functional esophageal disease. The main application of IEM occurs in the presence of myotomy and in the preparation of anti-reflux plasty. As far as myotomy is concerned, IEM can provide guidance in identifying a site for future intervention and, once accomplished, for documenting the completeness thereof. As far as anti-reflux plasty is concerned, it provides an opportunity to verify the onset of an anti-reflux high-pressure zone (nHPZ) that can be calibrated fittingly until the required values are achieved. IEM appears especially useful in effecting a Nissen fundoplication, the frightful complications of which compel many a surgeon to use other types of plasty, despite the lower rate of effectiveness. The perfect identity between the degree of loop closing and the manometric values obtained, and between the loop width and the length of the nHPZ, obtainable through Nissen's fundoplication only, testifies in favor of the use of IEM in preparation of this type of fundoplication only. The Authors present their case studies from 1985 to date, collected at the Service of Surgical Esophagology of the Faculty of Naples, covering 145 cases of Nissen's fundoplication, 70 of which after extramucosal cardias myotomy according to Heller, 54 cases of GER, including 2 cases of scleroderma, epiphrenic diverticula, DES and repeated surgery.