Background and objective: Acute renal failure is a serious complication of cardiac surgery. We studied the long-term survival and quality of life of patients requiring renal replacement therapy after cardiac surgery, since they represent a heavy burden on hospital resources and their outcome has never been adequately evaluated. Methods: Out of 7846 consecutive cardiac surgical patients, 126 (1.6%) required postoperative renal replacement therapy: their preoperative status and hospital course was compared with patients who had no need of postoperative renal replacement therapy. A multivariate analysis identified predictors of renal replacement therapy. Long-term survival and quality of life was collected in patients who had renal replacement therapy and in case-matched controls. Results: Hospital mortality in the study group was 84/126 (66.7%) vs. 118/7720 (1.5%) in the control population (P < 0.001). Patients who underwent renal replacement therapy and were discharged from the hospital (42 patients) had a reasonable long-term outcome: at 42 ± 23 months, 30 out of 42 patients were alive, with only 3 patients complaining of limitations in daily activities. Predictors of in-hospital renal replacement therapy were: emergency surgery, preoperative renal impairment, intra-aortic balloon pumping, reoperation for bleeding, previous cardiac surgery, female gender, low ejection fraction, bleeding >1000 mL, chronic obstructive pulmonary disease and age. Conclusions: This study confirms that the in-hospital mortality of patients requiring renal replacement therapy is high and shows a low long-term mortality with reasonable quality of life in patients discharged from hospital alive.