Acute massive intestinal bleeding from Crohn disease occurred in 1.4% of 503 patients undergoing treatment at the New York Hospital-Cornell Medical Center over a 43-year period. Of the entire series, 31% had clinically evident rectal bleeding, while 13% had occult bleeding. Combined with previously reported series, onset of massive bleeding was not influenced by age of patient, duration of Crohn disease, use of corticosteroids, or activity of disease. Surgical therapy gave satisfactory results in patients with life-threatening hemorrhage.