Laparoscopic Nissen fundoplication (LNF) is an effective treatment for gastroesophageal reflux disease; however, some patients develop dysphagia postoperatively. Manometry is used to evaluate disorders of peristalsis, but has not been proven useful to identify which patients may be at risk for postoperative dysphagia. Multichannel intraluminal impedance (MII) evaluates the effective clearance of a swallowed bolus through the esophagus. We hypothesized that MII combined with manometry may detect those patients most at risk of developing dysphagia after LNF. Between March 2003 and January 2007, 74 patients who agreed to participate in this study were prospectively enrolled. All patients completed a preoperative symptom questionnaire, MII/manometry, and 24-h pH monitoring. All patients underwent LNF. Symptom questionnaires were administered postoperatively at a median of 18 months (range: 6-46 months), and we defined dysphagia (both preoperatively and postoperatively) as occurring more than once a month with a severity >or=4 (0-10 Symptom Severity Index). Thirty-two patients (43%) reported preoperative dysphagia, but there was no significant difference in pH monitoring, lower esophageal sphincter pressure/relaxation, peristalsis, liquid or viscous bolus transit (MII), or bolus transit time (MII) between patients with and without preoperative dysphagia. In those patients reporting preoperative dysphagia, the severity of dysphagia improved significantly from 6.8 +/- 2 to 2.6 +/- 3.4 (P < 0.001) after LNF. Thirteen (17%) patients reported dysphagia postoperatively, 10 of whom (75%) reported some degree of preoperative dysphagia. The presence of postoperative dysphagia was significantly more common in patients with preoperative dysphagia (P= 0.01). Patients with postoperative dysphagia had similar lower esophageal sphincter pressure and relaxation, peristalsis, and esophageal clearance to those without dysphagia. Neither MII nor manometry predicts dysphagia in patients with gastroesophageal reflux disease or its occurrence after LNF. The presence of dysphagia preoperatively is the only predictor of dysphagia after LNF.