To provide improved inotropic agents for enhanced therapy of severe congestive heart failure (CHF), the hemodynamic efficacy of prenalterol (PN), a recently developed cardioselective beta-1 receptor agonist, was evaluated by cardiac catheterization in nine patients with refractory CHF due to chronic coronary disease. PN (4.8 mg intravenously) markedly augmented the cardiac index from 1.9 to 2.6 L/min/m2 (p less than 0.01) and substantially elevated stroke index from 24 to 30 ml/beat/m2 (p less than 0.001). Additionally, PN raised stroke work index 21 to 26 gm.m/m2 (p less than 0.005) and decreased total systemic vascular resistance from 1,702 to 1,260 dynes-sec cm(-5) (p less than 0.001). Concomitantly, heart rate, mean blood pressure, and left ventricular filling pressure were unaltered ( p greater than 0.05). Importantly, the heart rate-systolic blood pressure product was unchanged (p less than 0.05), and precipitation of cardiac dysrhythmias or myocardial ischemia was not observed. Thus PN produced considerable improvement of depressed cardiocirculatory performance without untoward effects and thereby appears a valuable new cardiotonic in the clinical management of severe low output ventricular dysfunction.