Prostacyclin, endothelin-1, and nitric oxide pathways are involved in the pathogenesis of pulmonary arterial hypertension. This devastating disease of the pulmonary vasculature is associated with vasoconstriction, thrombosis and proliferation, and this may be partly due to lack of endogenous prostacyclin secondary to prostacyclin synthase downregulation. Prostanoids (prostacycin analogues) are potent vasodilators and possess antiaggregant, antiinflammatory and antiproliferative properties. The first agent to be approved for the treatment of pulmonary arterial hypertension was epoprostenol. In the last decade other prostanoids (treprostinil, iloprost) has been approved for the treatment of pulmonary arterial hypertension.