As compared with normal 30 males and 25 females as controls, 80 males and 53 females with essential hypertension were studied for mechanocardiogram by hand grip exercise. At rest, the hypertensive group as against the normal group showed an increment of PEP, ICT, PEP/LVET and A/E-0 ratio, and shortening of LVET without any significant difference. Hand grip exercise augmented LVET and A/E-0 ratio, and reduced in PEP/LVET with a rise in blood pressure and heart rate. The hypertensive group with severe ECG changes showed, at rest, shortening of LVET and increases in PEP, ICT, and PEP/LVET. No definite tendency was observed in A/E-0. As compared with the normal group, decrease in PEP, ICT and PEP/LVET and increase in LVET and A/E-0 ratio were observed during the exercise, regardless of the degree of ECG changes. The more severe in ECG changes, the more increment in A/E-0 ratio was seen during the exercise. The recovery of each index after the cessation of the exercise showed a tendency to delay further according to increased ECG changes. Such a different response to the exercise in the hypertensives may be ascribed significantly to the hyperreactivity to catecholamine of hypertensive patients with high plasma level of catecholamine and to the elevated left ventricular end-diastolic pressure due to left ventricular hypofunction in advanced hypertension.