Abstract. Terbutalin, a β-mimetic drug, appears to have a favorable β2: β1 ratio. It is suitable for uterine relaxation. Ten normotensive pregnant women with imminent premature labor were studied during intravenous infusion of terbutalin with the non-invasive method of quantitative sphyg-mometry. Cardiac output increased and total peripheral resistance decreased. As there was only slight variation in the arterial blood pressure, terbutalin is indicated especially in cases with hypotension.