An obstruction index to estimate the left ventricle outflow gradient from the echocardiogram in patients with obstructive cardiomyopathies is proposed. It is based on the measurements of the mean distance between septum and anterior mtral valve leaflet, the total time of narrowing and the time of minimal and maximal narrowing. In the first group of patients studied, it seems to correlate fairely with the severity of clinical picture and with the gradient found at catheterization.