Using digitized M-mode echocardiograms and 24-h ambulatory blood pressure (BP) monitoring, we compared the effects on left ventricle (LV) and BP of 6-month treatment with a calcium antagonist or an angiotensin-converting enzyme (ACE) inhibitor in 36 hypertensive patients with LV hypertrophy (group 1, 18 subjects treated with sustained-release isradipine; group 2, 18 subjects treated with perindopril). At the basal evaluation, the two groups had comparable BP and LV parameters. After treatment, both groups showed a similar and significant reduction in 24-h, day- and night-systolic and diastolic BP (SBP, DBP). The reduction in LV mass index was greater (p < 0.01) in group 2. In group 1, percentage of decrease of LV mass correlated significantly with percentage of decrease in 24-h and daytime BP; this was not true of group 2. Together with the reduction in LV hypertrophy, there was a significant increase of peak lengthening rate of LV diameter that was greater (p < 0.01) in group 1. Both drugs can reduce LV hypertrophy and improve diastolic function. The reduction of hypertrophy induced by perindopril appears to be partly independent of BP decrease and therefore partly related to a direct action of perindopril on the myocardium.