The antihypertensive effect of a new non-selective .beta.-adrenergic blocking compound, penbutolol (40 mg twice daily), was compared with propranolol (160 mg twice daily) in 20 hypertensive patients using a double-blind cross-over scheme. Both compounds reduced both the supine and the standing blood pressure significantly. The magnitude of the responses did not differ significantly and both compounds evoked a commensurate decrease in heart rate. No significant side-effects were noted and laboratory tests did not disclose any biochemical changes.