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We sought to compare reflux and symptom association patterns in patients with nonerosive reflux disease (NERD), erosive esophagitis (EE), and in healthy volunteers (HVs).Patients with EE and NERD underwent combined impedance–pH monitoring. Normal values were defined on the basis of previously collected data from 48 HVs. We evaluated distal esophageal acid exposure time (AET), number and type of reflux episodes (acid, nonacid), acid and bolus clearance times, proximal extension of reflux episodes, and symptom association probability (SAP).Distal AET (percentage time, pH<4) was higher (P<0.01) in 58 EE patients (median 7.4%, 25–75th percentile 4.2–9.9%) compared with 168 NERD patients (4.2% (1.2–6.4%)) and 48 HVs (0.7% (0.2–1.4%)). Patients with EE and NERD had a higher (P<0.01) number of acid reflux episodes compared with HVs (51 (37–66) vs. 34 (22–51) vs. 17 (8–31);P<0.05), but a similar number of nonacid reflux episodes (22 (15–39) vs. 23 (15–38) vs. 18 (14–26);P=NS). The percentage of reflux episodes reaching the proximal esophagus was higher (P<0.01) in EE patients (57% (45–73%)) than in NERD patients (45% (36–60%)) and HVs (33% (19–46%)). A positive SAP for heartburn or regurgitation was found in 161 of 168 (96%) NERD and 54 of 58 (93%) EE patients (P=NS).Acid reflux episodes, volume, and acid clearance are important factors in the pathogenesis of reflux-induced lesions. Nonacid reflux contributes less to esophageal mucosa damage, but is involved in the development of reflux symptoms in both NERD and EE patients.