Objective: Previous studies have reported that LV hypertrophy (LVH) is related to LV dyssynchrony at rest. Impaired exercise tolerance with dyspnea is common in hypertensive patients with LVH and this may be due to the exaggeration of nonuniform ventricular activation during exercise. The aim of the study was to evaluate the effect of LVH on systolic intraventricular dyssynchrony during exercise. Design and method: A total of 58 patients with relatively well controlled hypertension who complained of exertional dyspnea were enrolled. (mean age: 55.5 짹12.1 years) Twenty patients were classified as having LV hypertrophy.(>115g/m2 for men, 95g/m2 for women) Exercise stress echocardiography was performed using a symptom limited, multistage supine bicycle exercise test. To evaluate the dyssynchrony of LV, we calculate the standard deviation (SD) of the averaged time-to-peak systolic velocity (TPS-SD, ms) of 12 middle and basal LV segments obtained from the three standard apical views at rest and peak exercise. Results: There was no significant difference in terms of gender, proportion of patients having DM, exercise duration and hemodynamic variables such as systolic BP, diastolic BP and HR between the two groups. LV mass index and left atrium (LA) volume index was higher and E/E��� (an index of diastolic filling pressure) was elevated at exercise in LVH group. TPS-SD was significantly higher in patients with LV hypertrophy at rest (32.6짹10.9 vs. 23.8짹12.1ms, p=0.011) with exaggeration of the degree of LV dyssynchrony at peak exercise. (41.4짹13.0 vs. 25.1짹12.9ms, p<0.001) Multiple regression analysis showed that LV mass index was independently associated with LV dyssynchrony at peak exercise(棺=0.515, P=0.001) when controlled for age, sex, systolic BP at peak exercise, LV ejection fraction. Conclusions: Intraventricular systolic dyssynchrony during exercise is significantly associated with the degree of LVH in patients with hypertension. This may be one of the possible mechanisms for exaggerated symptoms of exercise intolerance in patients with hypertensive LVH.