The haemodynamic effects of dobutamine were studied in 14 patients with chronic congestive cardiac failure. Heart rate, central venous, pulmonary arterial, pulmonary wedge, and aortic pressures, aortic dp/dt, cardiac output, cardiac index, stroke volume, and pulmonary and systemic vascular resistances were measured or derived. Dose-response curves were obtained by recording all measurements before and after intravenous infusion of dobutamine at rates of 2.5, 5, and 10 mug/kg per min for periods of 30 minutes each. Significant increases in mean values were observed for cardiac output from 3.7 to 6.4 l/min (82%), for stroke volume from 44 to 64 ml (39%), and aortic dp/dt from 692 to 1414 mmHg/s (92.0 to 188.1 kPa/s (76%). Heart rate increased only moderately from 86 to 101 per minute (31%). Significant reduction occurred in pulmonary wedge and central venous pressures. Mean aortic and pulmonary pressures did not change significantly, as a measure of decreased vascular resistances. The drug was uniformly well tolerated. The predominant inotropic effects of dobutamine without tachycardia or arrhythmias may be valuable in severe heart failure.