The acute effects of oral administration of niludipine (Bay a 7168), a new dihydropyridine derivative Ca2+-antagonist, on blood pressure (BP), hemodynamics and plasma renin activity (PRA) were investigated in patients with essential hypertension (n = 28) and normotensive volunteers (n = 7). In the hypertensives, BP was acutely lowered by 20 mg of niludipine (from 163/94 to 141/83 nmHg at 2 h, n = 7), 40 mg (163/101 to 140/90), and 60 mg (173/106 to 135/85). Niludipine (60 mg) increased cardiac output (CO; 5.13 to 7.56 l/min), stroke volume (79.0 to 107 ml/beat), and decreased total peripheral resistance (22.3 to 13.6 mmHg/l/min). In the normotensives, BP was not appreciably affected by 60 mg (decrease from 112/73 to 110/68). Heart rate (HR) and PRA were not influenced by the drug in all subjects. Long-term trials were carried out on 21 hypertensives. BP was reduced by niludipine monotherapy (20 mg, 4 times a day) from 167/97 to 140/80 mmHg at the 4th week and remained stable during the entire treatment. Addition of propranolol (10 mg, 4 times a day) did not lower BP any further, but tended to reduce HR. By adding penfluzide (2.5 mg a day) to this regimen, systolic BP was further lowered. Tachycardia, bradycardia, edema, increase in PRA or tachyphylaxis were not observed during the trial. The results indicate that niludipine, either alone or combined with propranolol and penfluzide, is effective in the treatment of patients with essential hypertension.