Ten young healthy volunteers were given placebo, propranolol (20 or 40 mg), nicergoline, an alpha blocking agent (30 mg) or the association of nicergoline (15 mg) and propranolol (20 mg) in a randomized double blind study. The results show that nicergoline potentiates the cardiodepressant action of propranolol, whereby the effects of 20 mg become the same as those of 40 mg given alone on cardiac output and myocardial oxygen demand, though the plasma propranolol levels are not changed. We, therefore, propose that nicergoline blocks alpha 1 agonist effects of propranolol, which are usually masked by the greater beta 1 blocking effects but could have clinical and therapeutic relevance.