Frequency analysis of first heart sound in elderly and expired cases was performed to reveal changes of the cardiovascular system accompanying aging. The vibration was analyzed for isometric contraction phase or 0.06 seconds following the main vibration of first sound by means of fast Fourier transform technique, and main frequency was compared. Mean main frequencies were 43.0 +/- 15.4 cps (mean +/- SD) in 21 cases from 54 years to 69 years, 41.4 +/- 12.6 cps in 34 cases from 70 years to 79 years, 40.0 +/- 14.4 cps in 19 cases from 80 years to 89 years, and 44.2 +/- 4.5 cps in 4 cases from 90 years to 94 years. It was 44.4 +/- 8.0 cps in 6 cases with left ventricular hypertrophy (LVH) on ECG, and 37.2 +/- 7.5 cps in 18 cases without LVH. It was 35.7 +/- 6.5 cps in 9 cases who expired and 32.6 +/- 5.8 cps in cases of those who died within a year. Though mean main frequencies were almost equal in these groups, it is higher than that of younger subjects, which suggests stiffness of the cardiovascular system of the aged. It was suggested that the stiffness of the cardiovascular system is greater than the increase in cardiac weight of elderly subjects with LVH. Mean main frequency was low in subjects who dies within a year, which may be due to cardiomegaly.