Transmitral flow velocity pattern obtained by the pulsed Doppler technique reflects left ventricular (LV) diastolic function, but an increase in left atrial pressure pseudonormalizes the flow pattern and masks diastolic dysfunction. We propose an index to assess LV diastolic function using color M-mode Doppler echocardiography and the base-line shift technique. This index, flow propagation velocity, represents the average velocity of early diastolic LV filling flow from the mitral orifice to mid-ventricle. In patients with ischemic heart disease and dilated cardiomyopathy including those with pseudonormalized transmitral flow pattern, flow propagation velocity had a good correlation with the time constant of early diastolic LV pressure decay (Tau), indicating that flow propagation velocity is a useful noninvasive parameter of diastolic function which does not pseudonormalize. We also found a significant correlation between flow propagation velocity and Tau in hypertrophic cardiomyopathy patients in contrast to inadequate or no correlation between each of the conventional parameters and Tau. In addition, our recent data suggest that flow propagation velocity was distinctly decreased even in the patients with hypertension who did not show significant increase in LV mass index. Flow propagation velocity is a unique noninvasive parameter of LV diastolic function, which can sensitively and accurately detect the diastolic impairment in patients with different types of cardiac diseases with various loading conditions.