The acute hemodynamic effects of nisoldipine (Bay K552) in patients with essential hypertension were studied using nuclear ventriculography. In a cohort of 16 essential hypertension patients, an oral dose of 15 mg nisoldipine significantly lowered blood pressure within 20 min. The effect lasted at least 3 h. Blood pressure that was 160.5 +/- 20.3/108.0 +/- 10.1 mm Hg initially was reduced to 137.0 +/- 14.9/93.8 +/- 9.4 mm Hg at 3 h (P < 0.001). Cardiac output rose, total peripheral resistance fell and ejection fraction rose significantly. End systolic and end diastolic volumes did not change significantly with this dose of nisoldipine. The acute hemodynamic effects of 15 mg nisoldipine administered orally, measured by repeat nuclear ventriculography, were maintained during therapy for the 8 weeks of observation. Thus, nisoldipine is a powerful antihypertensive agent, significantly decreasing BP as well as total peripheral resistance and increasing cardiac index. This effect was prominent after 3 h and wore off about 12 h after each dose. Five of the patients had an initially high heart rate. To these patients propranolol was added in small doses (20-40 mg/day, mean 25 +/- 26 mg/day). This addition did not change the results when the patients were analyzed separately.