Barrett's esophagus is a condition in which intestinal metaplasia replaces a portion of the normal squamous epithelium lining the distal esophagus. It occurs as a consequence of chronic gastroesophageal reflux. Patients with Barrett's often have both lower esophageal sphincter dysfunction and impaired esophageal body motility, and therefore tend to have relatively severe reflux. In addition, it is likely that the composition of refluxed material is important in patients with Barrett's. There is increasing evidence that Barrett's and complications of Barrett's are related to duodenogastric rather than pure gastric reflux. By allowing continued duodenogastric reflux, acid suppression therapy may promote the development of Barrett's. On the other hand, a functioning fundoplication abolishes reflux, ends repetitive injury to the esophageal mucosa, and is associated with a decreased incidence of disease progression in patients with Barrett's compared with medical therapy. Barrett's is a premalignant condition, and all patients should undergo routine endoscopic surveillance. Patients with adenocarcinoma detected while on surveillance present at an earlier stage and have better survival than patients who present outside a surveillance program. In the future, mucosal ablation techniques may allow removal of the metaplastic epithelium and eliminate the risk of malignancy.