Twenty-four patients (aged 34-68), with mild to moderate essential hypertension, received 10 weeks of treatment with the new calcium-channel blocker PN 200-110. Eighty-six percent of the patients achieved goal blood pressure (i.e., sitting diastolic pressure less than or equal to 90 mmHg). The average reduction in sitting and standing systolic and diastolic blood pressure (-14 +/- 2/-15 +/- 1 mmHg, -14 +/- 3/-13 +/- 2 mmHg, respectively) was highly significant (p less than 0.001). No reflex tachycardia (sitting pulse 1 +/- 2 bpm; standing pulse 3 +/- 2 bpm) or weight change (-0.3 +/- 0.9 pounds) accompanied the hypotensive response. Although the fall in blood pressure was accompanied by a small but significant increment in plasma renin activity (0.5 +/- 0.2 ng/ml/hr [p less than 0.05]), no significant changes in plasma angiotensin II, aldosterone, or prostaglandin E2-metabolite occurred. There was no significant correlation between the fall in blood pressure and baseline (pretreatment) or stimulated (posttreatment) levels of plasma renin activity, angiotensin II, aldosterone, or prostaglandin E2-metabolite.