This study assessed the effects of an angiotensin-converting enzyme (ACE) inhibitor, perindopril, on the 24-hour blood pressure (BP) profile and hemodynamic responses to isometric exercise and mental stress in elderly hypertensive patients. We performed ambulatory BP monitorings and echocardiographic studies during hand-grip exercises and a mental stress test before and after the 10-week administration of perindopril in 11 elderly patients (mean age, 71.8 years). Office BP was significantly decreased by perindopril treatment. Both daytime and nighttime systolic BP decreased significantly without any change in circadian pattern (P < 0.05). Daytime diastolic BP was also significantly decreased by perindopril (P < 0.05); nighttime diastolic pressure was decreased, but this result was not statistically significant. The reduction in 24-hour BP was associated with a decreased left ventricular end-systolic dimension (P < 0.01) and an increased fractional shortening (P < 0.01), suggesting reduced afterload due to arterial dilatation. The left ventricular mass index was not changed by perindopril therapy, and neither were systolic and diastolic BP responses to the handgrip exercises. The increases in systolic BP during mental stress was augmented after perindopril therapy, although systolic BP during mental stress after treatment was significantly lower than before treatment (P < 0.05). These results indicate that perindopril is effective in reducing ambulatory 24-hour BP levels and is associated with improved systolic function caused by dilatation of resistance vessels.