Acute haemodynamic effects of molsidomine, antianginal drug with vasodilator properties, were evaluated in 12 male patients with chronic congestive heart failure in New York Heart Association functional class 3 or 4 (mean age 56 +/- 7 years; ischemic heart disease in 8 cases, dilated cardiomyopathy in 3 cases, heart disease of combined aetiology in 1 case). After sublingual molsidomine (4 mg: 6 cases; 8 mg: 6 cases) the following haemodynamic changes were observed: mean right atrial pressure - 35% (p less than 0.01), left ventricular filling pressure -30% (p less than 0.01), total pulmonary resistance -33% (p less than 0.01), pulmonary arteriolar resistance -32% (p less than 0.01), cardiac index -6% (p less than 0.05), stroke volume index -12% (p less than 0.05), stroke work index +18% (p less than 0.01), heart rate -6% (p less than 0.01), double product -10% (p less than 0.01) (Fig. 3). Peak haemodynamic effect was reached between 30 and 90 minutes, lasting till 180 minutes. Molsidomine acutely reduced preload, did not show side effects and was well tolerated. These results suggest that molsidomine might be used in the treatment of chronic congestive heart failure, especially if characterized by an increased right and left ventricular filling pressure.