Foreign bodies in the stomach and duodenum are usually accidentally swallowed by children, mentally ill patients, alcoholics, or persons with dentures. Swallowed foreign bodies are usually asymptomatic, and moved down the alimentary tract to be passed spontaneously without discomfort. There had been reported many kinds of foreign bodies, for example, metal fragments, fish bones and so on. A metal thread, which looks like a fishing hook in gastrointestinal tract as a foreign body, has never been reported in humans. A 62-year-old male patient was admitted due to abdominal discomfort for five days after eating raw fish. We performed gastroduodenoscopy and could find a thread penetrating to the anterior wall of duodenal bulb. It was removed by biopsy forcep. Herein, we report a case of a metal thread in duodenal bulb, which looked like a fishing hook. (Korean J Gastrointest Endosc 2001;22:178 - 181)