This issue reviews the various techniques and uses of esophageal function testing, including the Bernstein Test, Esophageal Acid Perfusion Test, Esophageal Acidity Test, Esophageal Function Studies, Esophageal Manometry, and Esophageal pH Monitoring. These tests are often used to help determine the cause of frequent heartburn or trouble swallowing and to determine whether chest pain is being caused by a problem with the esophagus.