Fractional time intervals during cardiac cycle were determined by means of the analyses of mechanocardiograms in 100 male patients with hypertension and 100 healthy males, which served as controls. The mechanocardiograms anyalyzed in this study were simultaneously recorded electrocardiograms, phoocardiograms, apexcardiograms and carotid pulse tracings. Of various time intervals during systolic in patients with hypertension, the mechanical systole(both C-D and C-A2 intervals), the isovolumic contraction time, the initial phase of ventricular contraction and the ventricular pressure elevation time were significantly prolonged, whereas the protodiastole was significantly shortened. The prolongation of the mechanical systole was caused primarily by the lengthening of the isovolumic contraction time, which resulted from the prolongation of the components of the latter, namely the initial phase of ventricular contraction and the ventricular pressure elevation time. During diastole, there were significant prolongation of the isovolumic relaxation time and the rapid ventricular filling period, and a significant shortening of the slow ventricular filling period. Among these time intervals, the mechanical systole(C-A2 inlerval), the isovolumic contraction time, the ventricular pressure elevation time and the isovolumic relaxation time showed significant positive correlation with blood pressure. On the other hand, the slow ventricular filling period was significantly negatively correlated with blood pressure. These facts suggested that the changes in these time intervals were related to increased afterload and/or resultant myocardial or hemodynamic alterations.