Barrett's esophagus denotes the presence of columnar epithelium in the esophagus instead of the usual stratified squamous epithelium. Barrett's esophagus had been thought to represent a mediastinal extension of the stomach in patients with a congenital short esophagus. Subsequent clinical and experimental data have established the abnormality as an acquired condition resulting from chronic gastroesophageal reflux. Although roentgenographic studies may show a mild-esophageal stricture or an esophageal ulcer, definitive diagnosis requires endoscopy with directed biopsy of erythematous mucosa in the esophagus, or manometrically guided biopsies for showing the presence of columnar epithelium above the lower esophageal sphincter. Although the origin of the cells causing this epithelium is still unclear, three distinct epithelial types have been found: atrophic gastric-fundic, junctional, and specialized columnar. Esophageal strictures and esophageal ulcers are complications associated with Barrett's esophagus, but its major significance is the association with the development of adenocarcinoma of the esophagus. Treatment of Barrett's esophagus is aimed at preventing gastroesophageal reflux with the additional need for close endoscopic surveillance for the development of dysplasia or early adenocarcinoma. Whether the diagnosis of Barrett's esophagus mandates anti-reflux surgery (fundoplication) remains controversial.