Twelve patients (pts) with coronary and/or valvular heart disease and preoperative creatinine clearance (Ccr) below 30 ml/min underwent cardiac surgery using cardiopulmonary bypass (CPB) with pulsatile (P:n = 7) and nonpulsatile (NP:n = 5) perfusion. Preoperative Ccr was 15.8 +/- 4.4 ml/min in the P group and 26.5 +/- 4.7 ml/min in the NP group. After surgery, the NP group showed significant increases in BUN and serum creatinine within a week, but the P group showed significant increase in BUN only. The NP group had a significant decrease in Ccr on the 7th postoperative day, but there was no significant change in the P group. Three patients, 2 from the NP group and one from the P group, died from complications (operative mortality: 14 vs 40%). These data suggested that P-CPB appeared to be advantageous in patients with preoperatively impaired renal function with low Ccr although many other factors might influence the outcome.