Barrett's esophagus is defined as the replacement of normal squamous epithelium of distal esophagus with specialized columnar epithelium. This condition is considered to be a premalignant lesion of esophageal adenocarcinoma. Barrett's esophagus is classified into long-segment (> or = 3 cm in length) and short-segment ( <3 cm in length). Detection of the former is more difficult. Adenocarcinomas arising from short-segment Barrett's esophagus are uncommon in Korea. Barrett's adenocarcinoma restricted to the mucosa can be treated by endoscopic mucosectomy. In recent years, endoscopic submucosal dissection for early esophageal cancer has been extensively applied because it is a reliable method to achieve en bloc resection. In this paper, we report a case of esophageal adenocarcinoma arising from ultrashort-segment Barrett's esophagus, which was successfully resected by endoscopic submucosal dissection.