Intravenous fluorescein is an accurate predictor of small bowel viability, but its effectiveness in assessing colon perfusion during aortic surgery has not been evaluated. Over a 10 year period 186 of 3,306 patients undergoing aortic reconstruction received 500 to 1000 mg of intravenous fluorescein intraoperatively to evaluate colon viability. Prior history of colectomy, hypogastric or mesenteric arterial occlusive disease, or ruptured aneurysm placed these patients at risk to develop ischemic colitis. Patients were operated on for aneurysmal disease (n = 94), occlusive disease (n = 66), or a combination of both (n = 26): 171 exhibited uniform normal perfusion patterns under Wood's lamp illumination, while in 11 it was "patchy." None of these patients developed full-thickness ischemic colitis (observed specificity: 100%). Fluorescence of the rectosigmoid was absent in four patients. One of these patients with a ruptured aneurysm underwent immediate sigmoid resection, while three underwent inferior mesenteric artery reimplantation. The fluorescein pattern subsequently normalized in two patients, but one underwent sigmoid resection for an expanding mesenteric hematoma. The second patient recovered without complications. The final patient continued to show a segmental sigmoid defect and postoperatively developed full-thickness injury requiring sigmoidectomy. During the same period 18 other patients developed transmural colon ischemia from 3,120 aortic reconstructions (0.6%), with a mortality rate of 56%. None had received intraoperative fluorescein. Selective use of intravenous fluorescein may reduce the mortality of ischemic colitis following aortic reconstruction.