Patients with end-stage liver failure, portal hypertension, and associated pulmonary artery hypertension (portopulmonary hypertension [PPHTN]) have a high mortality when undergoing liver transplantation. Successful transplantation in these patients may depend on efforts to reduce pulmonary artery pressure (PAP). To this end, a number of centers are using a continuous intravenous (IV) infusion of epoprostenol, which has been shown to improve symptoms, extend life span, and reduce PAP in patients with primary pulmonary hypertension. We report four cases in which treatment of patients with PPHTN with continuous IV epoprostenol was followed by the development of progressive splenomegaly, with worsening thrombocytopenia and leukopenia. This finding may limit the usefulness of epoprostenol in PPHTN and influence the timing of transplantation in such patients.