Renal fusion or ectopia can present formidable challenges during aortic surgery. To evaluate morbidity and define optimal management, the clinical histories of 20 patients with renal fusion or ectopia who underwent 21 aortic procedures at the authors' institution over a 37-year period were reviewed. Indications for surgery included aortic aneurysm in 16 patients (infrarenal in 15 and thoracoabdominal in one) and aortoiliac occlusive disease in five (with renovascular hypertension in two). The abnormal kidney was detected before surgery in 13 patients (65%) by excretory urography, arteriography, computed tomography, or ultrasonography. Arteriography revealed multiple and/or anomalous renal arteries in nine of 12 patients studied. At surgery, 15 patients (75%) were found to have multiple or anomalous renal arteries. Six required renal revascularization (reimplantation four, endarterectomy one, aortorenal bypass one). The renal symphysis was divided in two patients. There were no operative deaths. Six major complications included bleeding requiring reoperation, renal failure requiring short-term dialysis, pancreatitis, gastrointestinal bleeding, pneumonia and thrombophlebitis. Preoperative aortography is recommended in patients with renal fusion or ectopia because of the high incidence of associated renal artery anomalies. The surgeon must be prepared to preserve or revascularize these anomalous renal arteries. Division of the renal symphysis is rarely required. Although perioperative morbidity is raised, aortic reconstruction in patients with renal fusion or ectopia can be safely performed without increased mortality.