Background. The aim of this study was to evaluate whether baseline echocardiographic parameters can predict LV dysfunction on exercise echocardiography in patients with moderate to severe AR and normal resting LVEF. Methods. A symptom-limited treadmill exercise testing using the modified Bruce protocol was performed in 68 asymptomatic or mildly symptomatic patients with chronic moderate to severe AR patients (female 38.2%, 54짹14 yrs). Thirty patients had moderate AR, and 38 severe AR at resting stage. Clinical symptoms, vital signs, ECG, and 2-D/ Doppler hemodynamics were obtained during and/or immediately after exercise as well as at baseline resting stage. AR regurgitant volume was calculated using PISA method. Contractile reserve (CR) was defined as increase of EF after exercise. Results. The study populations were divided into 2 groups based on contractile reserve data after exercise echocardiography: 39 patients with CR and 29 patients without CR. There was significant inverse correlation between baseline regurgitatnt volume of AR, LVMI and change in ejection fraction(R=0.41, P<0.0001, R=0.46,P<0.001) on echocardiography after exercise.(figure) Age, LVIDd, LVIDs, LVMI, LVEDV, LVESV, RV were univariately predictive of contractile reserve. Multivariate stepwise regression analysis revealed that age (OR -0.221, P=0.016), LVMI (OR -0.98, P=0.009) and RV (OR -0.013, P=0.01) were independent predictors of contractile reserve. Conclusions. This study suggests that in patients with moderate to severe AR patients, larger regurgitant volume and larger LVMI are more likely to have early LV dysfunction after exercise.