Of 53 patients with horseshoe kidney (9 in the present series), 45 underwent operation for an abdominal aortic aneurysm: 40 electively and 5 on an emergency basis. The remaining eight patients underwent revascularization for arteriosclerosis obliterans. Of the 53 patients, 35 (66%) had renal artery anomalies. The anomalous arteries prevented aortic repair in 6 patients (17%), were left undisturbed in 9 (26%), were revascularized in 7 (20%), and were ligated in 13 (37%). Partial nephrectomy was required in 2 of the 13 patients undergoing arterial ligation. Symphysiotomy was performed in 16 (30%) of the 53 patients. The following approach to management of horseshoe kidney associated with disease of the abdominal aorta is suggested. 1. Whenever a horshoe kidney is suspected, excretory urography, aortography, and, if necessary, selective renal arteriography should be obtained preoperatively. 2. Anomalous renal arteries arising from resected segments of the aorta should be revascularized whenever technically possible, usually by reimplantation of the renal artery into the aortic graft. 3. If an anomalous renal artery is ligated, the kidney should be inspected for signs of ischemia, and partial nephrectomy should be performed if ischemia occurs. 4. Symphysiotomy should be avoided. If division is necessary, symphysiectomy is preferable to symphysiotomy. In either circumstance, care need be taken lest there be fusion of the urinary collecting system and the renal parenchyma. In most patients with horseshoe kidney, aortic surgery has been accomplished without complication and with only minor alteration in surgical technique, even when the renal anomaly is first detected at surgical exploration.