Peutz-Jeghers syndrome is a genetic disorder consisting of mucocutaneous pigmentation and gastrointestinal polyposis. Although the polyp may be found in a solitary fashion in this syndrome, such a case is exceedingly rare and would result in a case report even in other countries. A solitary Peutz-Jeghers polyp had not been reported domestically until now, and thereby, the authors here present a case of a clinical experience of Peutz-Jeghers syndrome with a solitary hamartomatous polyp in the duodenum. (Korean J Gastrointest Endosc 19: 796∼800, 1999)