The hemodynamic effects of urapidil were studied in 10 patients with secondary pulmonary hypertension investigated for the purpose of possible inclusion on a heart transplant waiting list. All patients gave their consent to participate. Nine patients had a dilated cardiomyopathy and 1 three-vessel coronary disease with diffuse hypokinesia. All were treated with digitalis, diuretics, converting enzyme inhibitors or calcium antagonists. Hemodynamic effects were measured 5 and 25 minutes after the slow intravenous injection of 50 mg of urapidil. Urapidil caused a significant decrease in pulmonary pressures (-20%) and total pulmonary resistance (-42.5%). The fall in systemic arterial resistance was of the same degree (41.5%). The fall in pulmonary arterial resistance was also significant (-26%). The increase in cardiac output was +35%, with no change in left ventricular myocardial function indices. Thus, in patients with congestive left ventricular failure and secondary pulmonary hypertension already treated with vasodilators, urapidil resulted in a hemodynamic improvement after intravenous administration, demonstrating a synergistic action with that of other vasodilators. This synergistic action could be used to test pulmonary arteriolar vasodilatation reserves during the hemodynamic assessment of patients in whom a heart transplant is contemplated.