Effects of continuous prostaglandin E1 (PGE1) infusion 0.03 micrograms.kg-1.min-1 on hemodynamics, body temperature and urine output during cardiopulmonary bypass (CPB) were studied. Systemic vascular resistance was kept significantly lower in PGE1 administration group than control group. Differences between core and peripheral temperature decreased faster in the PGE1 administration group than the control group. Mean arterial pressure was stable at 40mmHg during CPB in the PGE1 group and 60mmHg in the control group. However, there were no significant differences in urine output between the PGE1 administration group (10.8ml.kg-1.h-1) and the control group (9.4ml.kg-1.h-1). This study indicates that continuous PGE1 infusion (0.03 micrograms.kg-1.min-1) is a method of choice for vasodilation and improvement of peripheral perfusion during hypothermia of CPB.