Colonic ischemia, related to division of the inferior mesenteric artery during aortic surgery, can be a significant cause of postoperative mortality. Operative determination of collateral mesenteric blood flow during temporary occlusion of the inferior mesenteric artery by use of the Doppler ultrasound device was evaluated in 25 patients undergoing aortic reconstructive vascular procedures. In five patients, the evaluation confirmed arteriographic evidence of an occluded inferior mesenteric artery; however, collateral flow was audible at the base of the large bowel mesentery and serosal surface of the left colon. In the other 20 patients with patent inferior mesenteric arteries, temporary occlusion of the artery resulted in persistent audible collateral flow in eighteen. However, in the remaining two patients, temporary arterial occlusion resulted in loss of audible Doppler flow signals over the base of the mesentery and serosa of the left colon. Maintaining patency of the inferior mesenteric artery by proper placement of the aortic graft in one patient and reimplantation of the artery into the prosthesis in another resulted in a return of Doppler flow over the left colon. All patients did well post operatively. Our data suggest that the presence of audible Doppler flow over the base of the large bowel mesentery and serosal surface of the left colon may correlate with viability of the colon postoperatively. We recommend routine use of the Doppler ultrasound device to determine adequacy of collateral mesenteric blood flow in patients undergoing aortic reconstructive vascular procedures.