1 To examine the influence of age on beta-adrenergic receptor mechanisms, we have observed the cardiovascular, bronchial and metabolic effects of an intravenous infusion of the beta-adrenoceptor agonist terbutaline in healthy young and elderly female subjects (mean ages 20.9 and 72.1 years respectively). 2 There was a highly significant fall in systolic blood pressure in the elderly, in contrast to the rise in systolic pressure seen in the young subjects. A similar fall in diastolic pressure occurred in both groups, indicating comparable beta-adrenoceptor-mediated vasodilatation. The fall in mean arterial pressure was significantly greater in the old than in the young subjects. The increase in heart rate was significantly less in the elderly. 3 Changes in plasma glucose and potassium during the infusion were similar in the two groups. 4 The observed abnormality of myocardial sensitivity to beta-adrenergic receptor stimulation, which is not associated with a generalized blunting of beta-adrenoceptor mediated effects, may significantly impair autonomic cardiovascular regulation in the elderly.