We report a case of multiple duodenal, pancreatic, and gastric carcinoids. A 67-year old woman was admitted to our hospital for treatment of a duodenal carcinoid. Laboratory tests revealed that the patient was associated with macrocytic anemia and hypergastrinemia, and type A gastritis was shown by gastrofiberscopy. During surgery, another tumor was incidentally found in the head of the pancreas. The tumors in the duodenum and pancreas were completely excised by pancreatoduodenectomy and immunohistologically diagnosed as gastrin-and serotonin-producing carcinoids, respectively. Pathological examination revealed that in addition to the grossly found carcinoids, there were subclinical carcinoids, one of which was an endocrine cell micronest, located in the stomach and duodenum. The tumors in the duodenum, pancreas, and stomach showed different characteristics from one another morphologically and immunochemically. Although no definitive evidence has been obtained, some sort of genetic anomaly may have been involved in this case, and hypergastrinemia due to duodenal gastrinoma may induce multiple gastric carcinoids. A 67-year old woman was admitted to our hospital for treatment of a duodenal carcinoid. Laboratory tests revealed that the patient was associated with macrocytic anemia and hypergastrinemia, and type A gastritis. During surgery, another tumor was incidentally found in the head of the pancreas. respectively. The tumors in the duodenum and pancreas were completely excised by pancreatoduodenectomy and immunohistologically diagnosed as gastrin-and serotonin-producing carcinoids, respectively. Pathological examination revealed that in addition to the grossly found carcinoids, there were subclinical carcinoids, one of which was an endocrine cell micronest, located in the stomach and duodenum. The tumors in the duodenum, pancreas, and stomach showed different characteristics from one another morphologically and immunochemically. no definitive evidence has been obtained, some sort of genetic ano maly may have been involved in this case, and hypergastrinemia due to duodenal gastrinoma may induce multiple gastric carcinoids.