Background: Vasovagal syncope, i.e, neurally mediated syncope is common disorder in clinical practice. Previously, neurally mediated syncope has been known to result from mechanoreceptor discharge by vigorous ventricular contraction. However, recent studies showed that left ventricular ejection fraction(LVEF) during head-up tilt test(HUTT) showed an early pronounced decrease in patients with syncope. Therefore, we sought to evaluate hemodynamic change during HUTT with echocardiographic parameters. Methods: We evaluated 35 patients ( mean age 40 years ) with episode of unexplained syncope. Head up tilt table test was done at all patents. During the test, echocardiographic parameters ( LV dimension, EF, and mitral inflow pattern) were checked at each stage : at baseline, passive tiling 0, 20 minutes, tilting with isoproterenol 5, 15 minutes. Results: A positive response during the test was seen in 7 patients (20%). During the test, there was a similar, significant, progressive reduction of left ventricular end diastolic dimension and left atrial volume in all patients. However, LVEF decreased progressively in patients with positive test, whereas LVEF increased in patients with negative test. (figure). The ratio of mitral inflow E and early diastolic mitral annular velocity (E/E���) decreased after titling in patients with positive test. Conclusion: Hypercontractility of LV was not seen in patients with positive HUTT in this study. A decreased LV filling and impaired inotropic response may be an important contributory factor to vasovagal syncope.