Gastroesophageal reflux is a normal event, and the gastrointestinal tract possesses mechanisms to deal with the refluxed content so that symptoms are not produced. When the amount of refluxed material increases, or the quality changes, or one or more of the defense mechanisms breaks down, then the consequences occur in the esophagus. The variability of symptoms, of mucosal changes, and of motility patterns in response to pathologic gastroesophageal reflux imposes difficulties when one is trying to assess this disorder objectively.