Most esophageal malignancies are either squamous cell carcinomas or adenocarcinomas arising from Barrett's esophagus. We report a case of adenocarcinoma of the upper esophagus (cervical esophagus) that was derived from heterotopic gastric mucosa. In a 73-year-old man cervical esophagectomy was performed, followed by pharyngectomy, laryngectomy, and palliative dissection of lymph nodes on both sides of the neck, after an accurate diagnosis has been made by esophagography and endoscopy. The resected tumor was smoothly elevated (2.5 cm x 2.0 cm) and was microscopically identified as a well differentiated adenocarcinoma with invasion to the submucosa. The origin of the carcinoma was found to be a heterotopic gastric mucosa, by hematoxylin-eosin (H&E), immunohistochemical, and enzyme histochemical staining. To our knowledge, only 18 similar cases have been reported previously.