Barrett's esophagus is one of the terminal manifestations of reflux esophagitis. Although the typical Barrett's esophagus is very rare in Japan, the prevalence rate of short-segment Barrett's esophagus is extremely higher comparing with in western countries. The discrepancy may be caused by the differences of criteria of short-segment Barrett's esophagus. Observation of Barrett's mucosa in residual esophagus after esophagectomy is a useful method of considering the extension of Barrett's esophagus. Short-segment Barrett's esophagus accompanied by gastro-esophageal reflux may show a rapid extension under some adequate conditions. Large volume prospective studies are needed to clarify the extension speed of Barrett's esophagus.