Calcium-channel blockers are increasingly used as single agents for the treatment of essential hypertension. Following three weeks of single-blind placebo therapy, 43 patients with essential hypertension were randomized into four groups. Group 1 (10 patients) received placebo twice a day, Group 2 (13 patients) received darodipine (PY 108-068) 50 mg twice a day, Group 3 (9 patients) received darodipine 100 mg twice a day, and Group 4 (11 patients) received darodipine 150 mg twice a day. Patients were seen in the clinic weekly for 4 weeks. Clinical and laboratory evaluations were done on each patient. Darodipine caused a sustained decrease in the supine and standing systolic and diastolic blood pressure (p less than .001) and there were no significant pressure differences between the three drug dosages. The effects of the drug on heart rate were not consistent. Placebo had no effect on either blood pressure or heart rate. Side effects were few, mild, and consisted of headaches and peripheral edema, and did not necessitate discontinuation of the drug. No metabolic abnormalities were seen with either low or high doses of the drug. We conclude that: (1) darodipine is effective, safe, and well tolerated; (2) its antihypertensive effectiveness is similar at high and low doses, although the higher doses seemed to have a slightly greater effect on the diastolic arterial pressure; (3) the low dose may be preferable since side effects were dose related.