Ischemic enteritis is caused by either the interruption or significant reduction of arterial inflow to the small intestine. Risk factors are old age, diabetes mellitus and cardiovascular disease. It is very rare in young patients. We experienced a 21-year-old man with recurrent acute ischemic enteritis who was diagnosed with capsule endoscopy. He had previously taken medications for pulmonary hypertension and obstruction of both carotid arteries, and about 20 months earlier, he had been admitted due to hematochezia. Two sessions of angiography did not reveal the cause of hematochezia. At that time, capsule endoscopy showed mucosal edema and erythema in the terminal ileum, suggesting healed ischemic enteritis. The patient was admitted again due to hematochezia. Abdominal computed tomography showed focal celiac trunk stenosis and diffuse wall thickening of the small intestine, suggesting ischemic enteritis. Capsule endoscopy showed multiple active ulcers and severe hemorrhage with exudate, extending from the proximal jejunum to the terminal ileum. Using capsule endoscopy, the patient was diagnosed with acute extensive ischemic enteritis. Because endoscopic images of ischemic enteritis have rarely been reported, we report a case of a 21-year-old man who was diagnosed acute extensive ischemic enteritis with capsule endoscopy. (Korean J Gastroenterol 2013;61:160-165)