A Carcinoid tumor of the ampulla of Vater is extremely rare, accounting for less than 0.3% of all gastrointestinal carcinoids. Most reported cases have arisen from the gallbladder. An ampullary carcinoid most commonly presents with jaundice or upper abdominal discomfort, and bleeding from the tumor is exceedingly rare. A diagnosis is most frequently made postoperatively due to submucosal spread of the tumor. As the metastatic potential cannot be predicted by tumor size, a Whipple pancreaticoduodenectomy rather than local excision is considered the treatment of choice. We herein report a case of a primary carcinoid tumor located at the ampulla of Vater that presented as gastrointestinal bleeding; the tumor was diagnosed by an endoscopic biopsy after a papillary sphinterotomy. (Korean J Gastrointest Endosc 2007;35:420-423)