The purpose of this study was to validate the use of intraoperative manometry for assessing fundoplication and to search for predictive manometric criteria. This prospective study concerned 48 patients operated for gastroesophageal reflux. The manometry was carried out pre- and intraoperatively for all patients and postoperatively as well for 30 patients. The operative procedures were total fundoplication (n = 25) and posterior (partial) fundoplication (n = 5). The lower esophageal sphincter (LES) pressures and lengths were similar in the preoperative and intraoperative measurements before any esophageal mobilization, whereas the intraoperative LES pressure was significantly higher after fundoplication. The mean postoperative LES pressure decreased by 50 +/- 19% compared with the intraoperative pressure after fundoplication. The final intraoperative pressures of two dysphagic patients were not the highest of the study. More importantly, their final intraoperative pressures were 7.5 and 8.2 times the initial pressure, respectively, which was significantly greater than the intraoperative pressure increase of the nondysphagic patients (4.6 +/- 2.0 times). The final intraoperative pressure of the only patient with recurrence (18.2 mmHg) was the lowest of the study. In conclusion, intraoperative manometry is an effective method for evaluating the LES, and it could have predictive value for the surgical management of gastroesophageal reflux disease.