The present report concerns a patient who was first diagnosed as having adenoma in the duodenal bulb and subsequently was discovered to have adenomas in the stomach and colon. Surgical procedures including endoscopic resection could not be carried out because the patient had advanced liver cirrhosis. Follow-up colonoscopy no longer detected any polyp in the colon. Ultrasonography demonstrated a slowly growing hypoechoic mass in the liver, which was indicative of hepatocellular carcinoma. Then, single chemotherapy with oral administration of 5'-deoxy-5-fluorouridine was initiated. Surprisingly, repeated esophagogastroduodenoscopy revealed gradual regression of the gastric and duodenal tumors. Findings from the endoscopy and biopsy materials 10 months after the start of therapy showed disappearance of the gastric and duodenal adenomas. Despite enlargement of the hepatic mass, no recurrence of gastric and duodenal tumors has been noted during the past 1 1/2 yr.