The hemodynamic effects of dobutamine were compared with those of digoxin in seven patients with severe diffuse dilatative cardiomyopathy. Dobutamine (7.5 micrograms per kg of body wt per min) was given intravenously for 30 min and then discontinued until hemodynamics returned towards base line. Digoxin (12.5 micrograms per kg) was then given intravenously and hemodynamics were recorded for 120 min. Thereafter, dobutamine was again given at the previous dose. Dobutamine increased cardiac and stroke volume index and decreased pulmonary occlusive (wedge) pressure and systemic vascular resistance without changing heart-rate or arterial pressure. Digoxin also increased cardiac and stroke volume index and decreased pulmonary wedge pressure and systemic vascular resistance with digoxin without changing arterial pressure. In contrast to dobutamine, heart-rate was decreased with digoxin indicating reduced myocardial oxygen demand. Re-infusion of dobutamine did not have any notable hemodynamic effect, with the exception of an increase in heart-rate-systolic pressure production. These data indicate that the positive inotropic properties of digoxin and dobutamine are not additive. Furthermore, concerning the effect of digoxin on the heart-rate, its use seems preferable to the use of sympathomimetic agents such as dobutamine, in patients with diffuse chronic dilatative myocardiopathy.