The antihypertensive efficacy of amlodipine was studied in 22 patients (16 female, six male) with mild-to-moderate hypertension. Following an initial two-week placebo run in, patients with a sitting diastolic blood pressure in the range 95-115 mmHg (12.7-15.3 kPa) began the 12-week active treatment phase with amlodipine at a dose of 5 mg once daily. If the sitting diastolic blood pressure was not reduced to less than or equal to 90 mmHg (12.0 kPa) after four weeks' treatment, the amlodipine dose could be adjusted to 10 mg once daily. The final four weeks of active treatment comprised of a maintenance phase during which the dose, which had produced the desired therapeutic response in each patient, remained constant. At the end of the trial, 18 patients (85.7%) were classified as therapeutic successes (reduction in diastolic blood pressure to less than or equal to 90 mmHg [12.0 kPa] with a greater than or equal to 5 mmHg [0.7 kPa] from baseline values or a greater than or equal to 10 mmHg [1.3 kPa] decrease from baseline). Of these patients, 16 received the 5 mg dose throughout the study and only two required an increase to 10 mg once daily. Patients generally tolerated amlodipine treatment well.