Background: Modified ultrafiltration (MUF) has been demonstrated to have beneficial effects in children undergoing cardiac surgery with cardiopulmonary bypass (CPB). In adults, the hemodynamic effects of MUF are little known. The purpose of this investigation is to evaluate the hemodynamic effects of MUF in adult patients undergoing valvular heart surgery. Methods: 30 patients scheduled for elective mitral valvular surgery were randomized into either Ultrafiltration (U) or Control (C) group. In the U group, MUF was performed just after termination of CPB for 20 minutes, and not in the C group. Measurements of hemodynamic variables including right ventricular ejection fraction (RVEF) measured by thermodilution technique and hematocrit were performed before induction, just after termination of CPB, after completion of MUF and after sternal closure. Measurement after MUF in the C group was performed at 20 minutes after the termination of CPB. After transfer to ICU, same measurements were performed at postoperative 6 and 12 hrs. Results: After MUF, RVEF (P