Massive hemorrhage in the lower gastrointestinal tract, defined as bleeding distal to the ligament of Treitz at a rate in excess of 30 ml/hr, is most common in persons more than 50 years old. Most episodes stop spontaneously, although intervention to control the bleeding is needed eventually in 10-25% of patients. This review analyzes the use of scintigraphy, angiography, and interventional techniques in the diagnosis and treatment of these patients.