Background: Increased ventricular stiffness and afterload are major pathogenesis of heart failure. Objectives: We sought to investigate whether echo-Doppler derived ventricular elastance and ventricular-arterial coupling index can be helpful in predicting exercise capacity in patients with nonischemic dilated cardiomyopahty. Methods: Twenty three patients (59.4짹10.8 years, 11 men) with reduced systolic function (LV ejection fraction <40%) due to longstanding (> 6 months) nonischemic dilated cardiomyopathy underwent symptom limited graded supine bicycle exercise echo after comprehensive resting echo-Doppler evaluations. Left ventricular (LV) diastolic elastance was calculated as mitral inflow (E) and annular velocity (E���) to stroke volume (E/E���/SV) and ventricular-arterial coupling index (Ea/Ees) as arterial elastance index (end-systolic pressure/SV) to LV end-systolic elastance index (peak LV outflow tract velocity to acceleration time). Results: Mean LV ejection fraction was 27짹9%. Resting Ees was correlated with contractile reserve (��systolic mitral annular velocity to 25W. r=0.520, p=0.013). Ed correlated with Ea/Ees at rest (r=0.526, p=0.010) and during exercise (at 25W, r=0.042, p=0.571). In multivariate analysis resting Ed (棺=-0.584, p=0.003), Ea/Ees (棺=-0.505, p=0.007) and total stiffness index (Ed x Ea/Ees, 棺=-0.615, p=0.001) correlated with exercise duration independent of age and gender. Total stiffness index could reliably predict the impaired exercise capacity (<400 sec, 69% sensitivity and 70% specificity with 0.86). Conclusions: Ed and Ea/Ees, reflecting ventricular stiffness and ventricular interaction to afterload have close mutual relationship and value in predicting exercise capacity in patients with nonischemic dilated cardiomyopathy.