BACKGROUND: It has been known that pressure gradient(PG) between systolic radial arterial pressure(RAP) and systolic aortic pressure(AP) is often altered after cardiopulmonary bypass(CPB). In this study, we compared radial to femoral arterial pressure(FAP) difference between valve replacement(VR) group(n=189) and coronary artery bypass graft (CABG) group(n=90). METHODS: With IRB approval, anesthesia management followed the standard method for cardiac surgery. Heart rate, RAP, FAP, cardiac index(CI), forearm skin temperature, hematocirt and systemic vascular resistance index(SVRI) were recorded at before-CPB, after-CPB and after sternal closure. RESULTS: In CABG group, there was no change of PG between RAP and FAP before and after CPB. In VR group, systolic RAP was similar with FAP before CPB but the radial-femoral arterial pressure gradient was reversed with statistical significance after bypass. Compare with CAGB group, change of pressure gradient after CPB cousiderded statistical significant in valve replacement group. CI was increased and SVRI was decreased with statistical significance. CONCLUSION: In our study, patients in VR group who demonstrated high CI and low SVRI showed reversal of PG upon cessation of CPB. Reversal of PG at post-CPB probably partially depends on the degree of systemic vasodilation upon discontinuation of CPB.