Prostacyclin and its analogues (prostanoids) are potent vasodilators and possess 
antithrombotic, antiproliferative and anti-inflammatory properties. Pulmonary 
hypertension (PH) is associated with vasoconstriction, thrombosis and 
proliferation, and the lack of endogenous prostacyclin may considerably 
contribute to this condition. This supports a strong rationale for prostanoid 
use as therapy for this disease. The first experiences of prostanoid therapy in 
PH patients were published in 1980. Epoprostenol, a synthetic analogue of 
prostacyclin, and the chemically stable analogues iloprost, beraprost and 
treprostinil were tested in randomised controlled trials. The biological actions 
are mainly mediated by activation of specific receptors of the target cells; 
however, new data suggest effects on additional intracellular pathways. In the 
USA and some European countries, intravenous infusion of epoprostenol and 
treprostinil, as well as subcutaneous infusion of treprostinil and inhalation of 
iloprost, have been approved for therapy of pulmonary arterial hypertension. 
Iloprost infusion and beraprost tablets have been approved in few other 
countries. Ongoing clinical studies investigate oral treprostinil, inhaled 
treprostinil and the combination of inhaled iloprost and sildenafil in pulmonary 
arterial hypertension. Combination of other targeted therapies with prostanoids 
appears to be effective and safe. After 25 yrs of continued knowledge, 
prostanoids remain a mainstay in the treatment of pulmonary arterial 
hypertension.