Primary pulmonary hypertension (PPH) in patients with hepatic cirrhosis is often considered an unacceptable condition for liver transplantation because of increased morbidity and mortality during the procedure. We studied the incidence, characteristics, and final outcome of patients with PPH undergoing liver transplantation in our institution. Among the 226 patients undergoing 257 liver transplantations, eight (3.5%) fulfilled the conditions of PPH and responded to vasodilator therapy. Nitroglycerin 1.5 micrograms/kg produced a decrease in pulmonary vascular resistance index (PVRI) and mean pulmonary arterial pressure (MPAP) of 20% and 15%, respectively. Patients with PPH when compared with a matched group of patients without PPH had markedly increased hemodynamic changes in PVRI (P = 0.004) and MPAP (P = 0.0001) during and after the procedure. All patients with PPH required pulmonary vasodilator therapy after reperfusion of the new liver, while none in the group of patients without PPH required this therapy. Furthermore, after graft reperfusion, patients with PPH in which venovenous bypass was not used (n = 3), had a more compromised right ventricular function with a greater increase of central venous pressure (CVP) (90%) and MPAP (140%) when compared with patients with bypass or preservation of the recipient's vena cava (n = 5) in whom the increase of CVP and MPAP was 50% and 60%, respectively. Moderate PPH without a fixed level of pulmonary hypertension in patients undergoing liver transplantation is not related to an adverse outcome.