Left ventricular early diastolic phase analysis was carried out by simultaneous recordings of the electrocardiogram, phonocardiogram, apexcardiogram and the echocardiogram of the anterior leaflet of the mitral valve in 54 cases with the mitral stenosis. The following results were obtained: (1) The isovolumic relaxation period showed a close inverse correlation with the pulmonary capillary wedge pressure (r=-0.80, p (2) The period from point of nadir (O) to that of rapid filling (F) of the apexcardiogram showed a significant positive correlation with the mitral orifice area. However, O-F period showed no significant correlation with the pulmonary capillary wedge pressure. (3) In the cases of mitral stenosis, pulmonary capillary wedge pressure did not always change in parallel with mitral valve area. So, in evaluating the severity of mitral stenosis by phase analysis of early diastolic events in the left ventricle, it is important to use these parameters properly, namely, the isovolumic relaxation time for evaluation of the left atrial pressure and the O-F interval for evaluation of the mitral valve orifice area.