Over the past decade, there has been an alarming increase in the frequency of adenocarcinoma in Barrett's esophagus. These cancers are thought to evolve through a series of genetic alterations in the cells that comprise the Barrett's epithelium. The genetic alterations appear to involve activation of protooncogenes and dysfunction of tumor suppressor genes (eg, thep53gene), and result in morphologic changes recognizable as dysplasia. Dysplasia is widely regarded as the precursor of invasive cancer, and high-grade dysplasia in Barrett's esophagus frequently is associated with adenocarcinoma. Endoscopic surveillance can detect dysplasia and early, curable malignancies in Barrett's epithelium. Esophageal brush cytology and biopsy of Barrett's esophagus and both cytology and biopsy specimens should be obtained during surveillance endoscopic examinations.