Gastroesophageal reflux may be responsible for atypical extra-esophageal symptoms, such as chest pain, dyspnea, chronic cough, or hoarseness. Prospective studies of gastroesophageal reflux have indicated reflux as the cause for chronic cough in 10 to 20% of patients. The precise mechanism by which reflux causes cough remains uncertain, although the possibility that the cough is caused by stimulation of the esophageal mucosa receptors rather than aspiration is suggestive from some studies. Prolonged esophageal pH monitoring affords an opportunity to document objective gastroesophageal reflux. Furthermore, pH monitoring gives the opportunity to correlate temporally acid reflux events with the onset of certain symptoms.