Esophageal manometry is a physiologic test of esophageal function that complements endoscopy and provides a visual assessment of esophageal abnormalities. pH testing quantifies acid refluxing into the esophagus. pH/impedance testing detects acid, weakly acidic reflux, and alkaline reflux into the esophagus. Physiologic studies of the esophagus are predictive of a response to medical and surgical treatment and have an important role in evaluating patients who do not respond to therapy.