The aim of this study was to assess the effects of amlodipine in patients with mild-to-moderate primary hypertension and left ventricular hypertrophy. Nineteen patients (6 women, 13 men; mean age, 52 years) with primary hypertension were included in the study and all completed the study. After the 2-week, single-blind placebo phase, 5 mg/d oral amlodipine was initiated. If diastolic blood pressure (DBP) could not be reduced below the target level (less than or equal to 90 mm Hg) after 6 weeks of treatment, the dose of amlodipine was increased to 10 mg/d. Clinical evaluation was performed at weeks 0, 1, 2, 4, 6, 8, 10, 14, 18, 22, and 26, and echocardiography at the end of the placebo phase and at weeks 14 and 26. No significant reduction in blood pressure was recorded during the placebo phase. Systolic and diastolic blood pressures (mean +/- SE) were 163 +/- 20 mm Hg and 102 +/- 5.4 mm Hg, respectively, at the end of the placebo phase; these values were reduced to 139 +/- 19 mm Hg (P < 0.001) and 86 +/- 8 mm Hg (P < 0.001) at week 14. This reduction in blood pressure was maintained until the end of the study. No significant alterations were shown in heart rate during the study. DBP was reduced to less than or equal to 90 mm Hg in 10 (53%) of 19 patients with 5 mg/d and in 6 (32%) of 19 patients with 10 mg/d of amlodipine. Thus an overall therapeutic success of 84% was achieved. Left ventricular mass index (mean +/- SE) was 147 +/- 20 g/m(2) at the end of the placebo phase; it decreased to 129 +/- 20 g/m(2) at week 14 (P < 0.001) and to 123 +/- 19 g/m(2) at week 26 (P < 0.05 for the values at weeks 14 and 26). The mitral early filling flow velocity (wave E) to late filling flow velocity (wave A) ratio was significantly increased 0.7 +/- 0.1 to 0.9 +/- 0.2 at the end of the trial (P < 0.001). Echocardiographic assessment showed no statistically significant changes in left ventricular ejection fraction and cardiac index. It was concluded that amlodipine, given in single daily doses, is an effective antihypertensive agent in patients with primary hypertension, improving left ventricular diastolic function and reducing left ventricular hypertrophy.