We evaluated 1525 consecutive patients who had undergone thoracic or thoracoabdominal aortic surgery to ascertain the factors associated with the development of acute renal failure. Complete data were available in 1233 patients who were treated recently, and these were analyzed. Acute renal failure, severe enough to require dialysis, developed in 5.5% of this group (68/1233): 2.3% and 7%, respectively, for descending (9/391) and thoracoabdominal repairs (59/842). Of interest, on multivariate analysis, both renal artery endarterectomy for occlusive disease (p = 0.0006) and chronic dissection (p = 0.03) were associated with significantly less acute renal failure. On multivariate analysis, the significant independent predictors (p less than 0.05) of acute renal failure were preexistent renal dysfunction, evidence of diffuse atherosclerosis, the use of the pump bypass, and markers of hemodynamic instability. Contrary to earlier reports based on a smaller number of patients, we found that neither the use of pump bypass (7% acute renal failure), atriorenal bypass (8% acute renal failure), nor cold Ringer's lactate (3% acute renal failure) appeared to significantly avert the complication of acute renal failure. Indeed, pump bypass appeared to be deleterious (p = 0.0146) and perfusion with cold Ringer's lactate was not without risk. Furthermore, in a prospective evaluation of angiotensin converting enzyme blockers, we were unable to show that they afforded renal protection after transient renal ischemia. This study has clarified the clinical problems associated with acute renal failure and lays the foundation for future research.