The effects of exercise in combined aortic stenosis and insufficiency were evaluated in 10 patients by pressure measurements and the measurement of forward (QF) and regurgitant (QR) flows by simultaneous upstream and downstream sampling using indocyanine green. While heart rate increased, systolic aortic valve pressure gradient (mean, 37 ± 9 mm Hg) did not change. Increased QF(mean, 4.54 ± 0.34 at rest and 6.89 ± 0.42 liters/min with exercise,P< 0.001) was balanced by decreased QR(means, 4.09 ± 1.02 and 2.33 ± 0.71 liters/min,P< 0.02), and total flow did not change significantly. Although diastolic regurgitant period declined, total diastolic seconds per minute decreased by only 6%, while calculated systemic resistance decreased by 30%. Left ventricular systolic and aortic pressures increased, while left ventricular end-diastolic pressure and diastolic aortic valve gradients were unchanged. Mean systolic aortic valve area, calculated by utilizing total valve flow, was 1.8 ± 0.3 cm2in both states.Thus, exercise reduces regurgitant fraction in mixed aortic lesions as in pure aortic insufficiency. This observation confirms the necessity of measuring total valve flow in evaluation of mixed valve lesions. Reduced regurgitation primarily reflects an altered relationship of peripheral resistance to backflow resistance. While the stenotic valve is demonstrated to behave as a fixed systolic orifice, the diastolic aortic orifice area cannot be calculated from the Gorlin equation as it does not account for peripheral resistance.