Fifty-two cases of primary adenocarcinoma of the esophagus were studied with respect to their origin and features in the early stage. The origin of the tumor was determined in 12 cases. Six cases arose in Barrett's esophagus, 5 cases in esophageal glands, and one case in ectopic gastric mucosa. The postoperative prognosis was closely related to the invasion to the adventitia. Tumors with no adventitial invasion showed excellent results, and their early detection is recommended. Submucosal tumors arising in Barrett's epithelium or in leading ducts of esophageal glands presented as small elevated lesions at endoscopy. On the other hand, tumors arising in submucosal glands showed diffuse infiltration into the esophageal wall and were difficult to detect in the early stage. Endoscopic examination aided by the staining method or brush cytology is recommended.