The hemodynamic effects of oral bucindolol, a non-selective beta-adrenergic blocking agent with intrinsic sympathomimetic activity and direct vasodilating properties, were studied at rest and during handgrip exercise with a flotation-directed pulmonary artery catheter in 12 patients with mild to moderate essential hypertension. After the initial dose of 150 mg of bucindolol, blood pressure (BP) was significantly reduced and cardiac output was increased (from 5.9 +/- 0.8 to 6.8 +/- 1.6 liters/min) in the supine position and during exercise (p less than 0.05). Systemic vascular resistance was reduced (from 1,555 +/- 339 to 1,311 +/- 467 dynes s cm-5, p less than 0.01) at rest and without significant changes during exercise. There were increases in heart rate (13 +/- 13%, p less than 0.01) and right atrial (69 +/- 77%, p less than 0.05), pulmonary arterial (38 +/- 24 %, p less than 0.001) and pulmonary artery wedge pressures (62 +/- 46%, p less than 0.001) during exercise. Bucindolol did not change these variables at rest or during exercise. Bucindolol increased plasma norepinephrine levels both at rest (from 330 +/- 151 to 588 +/- 320 ng/liter, p less than 0.01) and during exercise (from 468 +/- 220 to 685 +/- 390 ng/liter, p less than 0.05). After 4 weeks of bucindolol with doses of 50 to 200 mg 3 times daily, BP was reduced in both supine and standing positions (mean arterial BP of 11 +/- 7% [p less than 0.001] and 11 +/- 6% [p less than 0.001], respectively), without changes in cardiac output, systemic vascular resistance or plasma norepinephrine level.(ABSTRACT TRUNCATED AT 250 WORDS)