['Pathological bolus exposure is defined in the present study as cases in which all reflux percentage times are above 1.4% of the total reflux number, as revealed by impedance-pH monitoring. The role of pathological bolus exposure in the pathogenesis of non-cardiac chest pain (NCCP) is poorly known. We aimed to classify and characterize NCCP using combined impedance-pH monitoring.', 'Seventy-five consecutive patients with NCCP were prospectively enrolled from January 2006 to October 2008. All the patients underwent upper endoscopy, esophageal manometry, and 24-h multichannel intraluminal impedance (MII)-pH metering.', 'Sixteen patients (21.3%) had esophageal erosion upon endoscopy. Upon esophageal manometry, 37 patients (49.3%) had esophageal dysmotility. When the patients were classified based on MII-pH metering, 16 (21.3%) showed pathological acid exposure, and 40 (53.3%) showed pathological bolus exposure. The DeMeester score of patients with pathological acid exposure was higher than that of patients with pathological bolus exposure (P = 0.002). There was no significant difference in age, sex, typical esophageal symptoms, presence of esophageal erosion, esophageal dysmotility, improvement with proton pump inhibitor medication, symptom index ≥ 50%, percentage of time clearance pH below 4 ≥ 4%, and all reflux time ≥ 1.4% in the fasting period between the two groups. When the patients were divided into gastroesophageal reflux disease (GERD)-related NCCP and non-GERD-related NCCP groups based on MII-pH metering and upper endoscopy, there was no difference between the two groups.'] Does pathological bolus exposure play a significant role in eliciting non-cardiac chest pain?