In 17 patients with coronary heart disease, hemodynamic measurements were performed before and after sublingual application of 10 mg isosorbide dinitrate (ISDN). 10 patients showed signs of heart failure with pulmonary congestion and a left ventricular filling pressure above 15 mmHg, resting hemodynamics were normal in 7 patients. Eight of the patients with left ventricular failure had sustained acute myocardial infarctions the size of which was assessed by serial determinations of serum creatine phosphokinase. Application of ISDN resulted in a significant decrease of systemic and pulmonary artery pressures and pulmonary capillary wedge and right atrial pressures of patients both with and without left ventricular failure. Cardiac index and stroke index as well as systemic and pulmonary resistances did not change significantly. ISDN did not affect left ventricular stroke work in patients with elevated filling pressures; however, a decrease of normal filling pressures was associated with a decrease of stroke work. Thus, in coronary patients with chronic congestive heart failure, sublingual application of nitrates results in a beneficial hemodynamic unloading. However, if the acute infarct size is taken into account, it can be demonstrated that hemodynamic improvement after ISDN--judged by the relation stroke work/filling pressure--becomes less pronounced with increasing infarct size.