Barrett's esophagus is a complication of chronic gastroesophageal reflux disease and can be diagnosed when there is an endoscopic abnormality in which a biopsy shows evidence of specialized columnar epithelium, characterized by the presence of acid mucin-containing goblet cells. Much of the controversy in this body of literature relates to the complex anatomy of the esophagogastric junction and the difficulty in precisely identifying this landmark at endoscopy. By definition, in Barrett's esophagus, the squamocolumnar junction is proximal to the esophagogastric junction. Although fundic-type or cardiac-type (junctional) columnar epithelium may be present in Barrett's esophagus, it is only the presence of specialized columnar epithelium that is diagnostic of this condition. Patients with Barrett's esophagus are at risk of progressing to esophageal dysplasia and adenocarcinoma. There are several problems with using dysplasia as a marker for increased cancer risk in these patients, including problems with sampling error and intra- and interobserver variation in the recognition of dysplasia. It may be difficult to distinguish regenerative epithelial changes from dysplasia, low-grade from high-grade dysplasia, and high-grade dysplasia from intramucosal adenocarcinoma. Finally, there are relatively few prospective data evaluating the natural history of high-grade dysplasia. The management of patients with Barrett's-related dysplasia is controversial and varies from institution to institution. Future emphasis should be on cost-effective techniques for sampling as much of the esophageal mucosa as possible in patients who are at the highest risk of progressing to dysplasia and adenocarcinoma. Identification of biomarkers that identify such patients before the histologic recognition of dysplasia will be an area of intensive research.