Cirsoid aneurysms (exulceratio simplex Dieulafoy) as a cause of massive gastrointestinal hemorrhage have been known to occur in the stomach. Endoscopy plays an important role in the diagnosis of and therapy for these lesions. We report two cases of a cirsoid aneurysm in the proximal jejunum; two cases have been previously reported in the literature. These lesions have the same pathologic features as gastric cirsoid lesions and cause massive gastrointestinal hemorrhage. Because these lesions are beyond the reach of current endoscopy, surgery was necessary to diagnose and treat the lesions in three of four patients. The fourth patient died after unsuccessful surgical exploration, and the lesion was found post mortem. Jejunal cirsoid aneurysms may be an unrecognized rather than a rare cause of gastrointestinal bleeding. They should be considered in the patient with massive proximal gastrointestinal bleeding in whom the source is not known, especially if angiography suggests a small-bowel site. With the advent of newer forms of endoscopy that can examine the small bowel, the management of these lesions may change; at present, surgery is lifesaving.