Acute renal failure requiring dialysis therapy after cardiac surgery occurs in 1% to 5% of patients; however, the optimal timing for initiation of dialysis therapy still remains undetermined. To assess the validity of early start of dialysis therapy, we studied the comparative survival between 14 patients who started to receive dialysis therapy when urine volume decreased to less than 30 mL/hr and another group of 14 patients who waited to begin dialysis therapy until the level of urine volume was less than 20 mL/hr for 14 days following coronary bypass graft surgery. Twelve of 14 patients who received early intervention survived. In contrast, only 2 of 14 patients in the late-dialysis group survived. There was a significant difference in survival between the two groups (p < 0.01). There were no significant differences between the two groups with respect to age, sex ratio, the APACHE (Acute Physiologic and Chronic Health Evaluation) II score, and the levels of serum creatinine at the start of dialysis therapy (2.9 +/- 0.2 mg/dL vs. 3.1 +/- 0.2 mg/dL), as well as the levels of serum creatinine at admission. We propose that the timing of the start for treatment of acute renal failure following cardiac surgery should be determined by the decrease of urine volume and not the levels of serum creatinine. Early start of dialysis therapy may help improve the survival of patients with acute renal failure following cardiac surgery.