Fifty patients with massive lower gastrointestinal bleeding were initially managed with emergency angiography. The average age was 67.2; mean hematocrit, 23.7; and average transfusion, 7.6 units. Thirty-six patients (72%) had bleeding site located; bleeding sites were distributed throughout the colon. Etiologies of bleeding included diverticular disease (19 patients) and arteriovenous malformations (15 patients). Twenty of 22 (91%) patients receiving selective intra-arterial vasopressin stopped bleeding; however, 50% rebled on cessation of vasopressin. Thirty-five of 50 (70%) patients underwent surgery, with 57% operated on electively after vasopressin therapy. Seventeen patients had segmental colectomy, with no rebleeding. Nine of the 17 patients had diverticular disease in the remaining colon. Operative morbidity in these 35 patients was significantly improved when compared to previously reported patients undergoing emergency subtotal colectomy without angiography (8.6% vs. 37%) (p less than 0.02). Emergency angiography successfully locates the bleeding site, allowing for segmental colectomy. Vasopressin infusion transiently halts bleeding, permitting elective surgery in many instances.