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Background: Determining a causal relationship between abnormal reflux into the proximal esophagus/pharynx and extraesophageal manifestations of gastroesophageal reflux disease(GERD) remains a diagnostic challenge. In this study we aim to determine whether pharyngeal pH monitoring provides superior sensitivity over dual-channel pH testing in detecting laryngopharyngeal reflux(LPR).Methods: 7 control subjects and 17 symptomatic patients, 4 with typical GERD and 13 with primary respiratory symptoms, underwent 24-hour ambulatory esophageal multichannel intraluminal impedance(MII)-dual pH simultaneously with pharyngeal pH monitoring. The distal pH sensor was placed 5cm above the manometrically determined upper border of the lower esophageal sphincter(LES) and the proximal 15cm above. Pharyngeal pH was monitored concomitantly using a separate pH probe positioned 1cm below the uvula. Data collection was synchronized between the devices. Esophageal reflux was considered present if pH dropped to <4 in either pH sensor, and/or a drop occurred ≥50% from baseline in impedance 3, 5, 7 or 9cm above LES(distal) or 15 and 17cm above LES(proximal). Separate pH thresholds of <5.5, 5.0, 4.5 and 4.0 were defined for reflux episodes detected in the pharyngeal probe. Results: At a threshold of pH<5.5, an average of 1(±4) pharyngeal reflux event over 24 hours was seen in control subjects. Symptomatic patients had greater pharyngeal pH exposure than controls, averaging 7(±14) episodes/24 hours in those with typical GERD symptoms and 46(±76) in those with respiratory symptoms. Total pharyngeal reflux events(603) were markedly more common in patients with respiratory symptoms than either control(10) or typical GERD symptoms(28). Further, the highest number of pharyngeal reflux episodes recorded across all pH thresholds was observed in subjects presenting with primary respiratory symptoms: 603, 91, 38 and 40 events at pH<5.5, 5.0, 4.5 and 4.0, respectively. 6 of the 11 patients with abnormal distal pH results had corresponding abnormal pharyngeal acid exposure; however, only 3 had concomitant positive proximal esophageal pH results. Pharyngeal pH also appears superior to the proximal esophageal pH in differentiating GERD related respiratory symptoms, as compared to gastrointestinal. Fundoplication normalized pharyngeal pH and markedly relieved symptoms in a single patient with severe respiratory symptoms and normal proximal esophageal acid exposure.Conclusions: The more common prevalence of pharyngeal reflux, as compared to proximal esophageal reflux, particularly in subjects with extraesophageal symptoms, suggests that pharyngeal pH monitoring may be a more sensitive diagnostic tool for LPR than proximal pH monitoring. Symptom relief and pharyngeal pH normalization post fundoplication provides further evidence of the utility of ambulatory pharyngeal pH monitoring.