Cardiac -receptor responsiveness is diminished by both ageing and hypertension. However, concomitant decreases in the activity of counter-regulatory mechanisms, such as the arterial baroreflex and neuronal catecholamine uptake influence the ultimate cardiac responses to adrenergic agents in vivo. In the present study, we evaluated by echocardiography cardiac responses to intravenous infusion of epinephrine in 14 young and 18 older normotensive subjects, and 10 young and 17 older hypertensive subjects. To assess the relative contribution of intrinsic cardiac and counter-regulatory components to the overall response, in the young groups infusions were repeated combined with a ganglionic blocker. Epinephrine induced increases in heart rate were similar in the 4 groups. Increases in stroke volume, ejection fraction and cardiac index were similar in the 2 hypertensive groups and young normotensives. In contrast, they were attenuated in the older normotensive group resulting in higher LV responses in older hypertensive than normotensive subjects. Heart rate and LV responses to epinephrine in the presence of ganglionic blockade did not differ between the 2 young groups. Increases in plasma norepinephrine due to epinephrine infusion were larger in hypertensive than normotensive subjects. One may conclude that compared to young normotensives in hypertensive subjects mechanisms increasing versus decreasing cardiac responses to epinephrine may remain in balance, and compared to older normotensives older hypertensive subjects exhibit enhanced cardiac responses to sympathetic stimulation.