The effect of 4 mg Molsidomine iv. followed by a continuous infusion of 3 mg per hour for 3 hours on arterial blood pressure, pulmonary artery pressure, cardiac index, peripheral and pulmonary vascular resistance and heart rate was evaluated in eleven patients suffering from chronic heart failure caused by non-ischaemic dilatative cardiomyopathy (NYHA II-III). A significant decrease in systemic blood pressure, systolic and mean pulmonary artery pressure and pulmonary wedge pressure was observed and also a marked decrease in total peripheral and pulmonary vascular resistance. There was a slight, but not significant increase in cardiac index. The heart rate did not change significantly. Treatment had to be stopped in one patient because of side effects (hypotension, nausea).