We experienced a case of acute duodenal ulcer after reconstruction by a gastric tube for a hypoharyngeal cancer in a 72-year-old man. There were previous histories of undergoing, a pharyngolaryngectomy and bilateral modified neck dissection for a hypopharyngeal cancer in September 1992, and additional pharyngectomy and esophagectomy wihtout thoracotomy with esophageal replacement via retromediastinal route by means of a gastric tube in January 1993. He had used non-steroidal anti-inflammatory drugs for light femoral pain and ischial pain since October 1994. An upper gastroendoscopic examination revealed active ulcer on the bulbus of the duodenum and ulcer scar on the middle of the gasric tube in October 1995. The serum gastrin value was normal and the blood flow of mucosa of gasric tube was good. In contrast, 24 hours pH monitor revealed the high acidity in the pylorus and low acidity in the corpus of the gastric tube. He was treated medically and the clinical course was good. We presum that in this case, the ulcer was caused by the use of non-steroidal anti-inflammatory drugs and restoration of acid secretion ability. Further investigation is needed to clarify the cause of the difference in acid secretion in the gastric tube.