The pharmacological profile of nebivolol (N), a chemically novel β-adrenergic antagonist, was assessed in investigations on isolated tissues, awake spontaneously hypertensive rats (SHR), closed-chest anesthetized dogs, and humans. In vitro, N was found to be a potent antagonist of β1-adrenergic receptors (A2 value, 5.8 × 10−9M) and only a weak β2-adrenergic antagonist (A2 value, 1.7 × 10−6M). The selectivity for the β1-adrenergic receptor was higher for N than for any of the reference compounds. In dogs—similarly with atenolol—N was more potent in blocking the isoprenaline (I)-induced increases in left ventricular performance than the I-induced decrease in arterial pressure. In dogs, as compared with propranolol, N (0.025 and 0.01 mg · kg−1 i.v.) increased cardiac output and stroke volume, lowered systemic vascular resistance, and had no significant effect on the variables related to left ventricular contraction. In contrast to other β-adrenergic antagonists, N acutely lowered arterial blood pressure in SHR (1.25 mg · kg−1 i.p.) and in hypertensive patients (1 oral dose of 5 mg) for several hours. In healthy volunteers N (5 mg) lowered systemic vascular resistance during daily oral treatment and did not negatively affect left ventricular function. In conclusion, N is a potent and selective β1-adrenergic blocking agent with an interesting hemodynamic profile. In hypertensive subjects and SHR, a single dose lowers arterial blood pressure for substantial periods of time.