Twenty patients (12 males, 8 females, mean age 51 +/- 10 years) with mild to moderate arterial hypertension were treated with nitrendipine (mean daily dose 17 mg) during a 6 month period. Patients were evaluated with blood measurement and with 24-hour ambulatory blood pressure monitoring. In 16 patients who completed the study, systolic and diastolic blood pressure decreased of 13-15% and 18-20% respectively after at least 1 month of therapy. Mean 24-hour blood pressure was reduced of 9.7% (p < 0.01) at the end of the third month and of 13.9% (p < 0.01) at the end of the sixth month. Both systolic and diastolic 24-hour blood pressure were significantly reduced. Nitrendipine was active on day time and night time pressure. Only 1 patient had edema of the legs. Heart rate was not increased by the drug. Total cholesterol and LDL cholesterol were reduced.