Prostacyclin is a powerful cardioprotective hormone released by the endothelium of all bloodvessels. Prostacyclin exists in equilibrium with other vasoactive hormones and a disturbancein the balance of these factors leads to cardiovascular disease including pulmonary arterialhypertension. Since it's discovery in the 1980s concerted efforts have been made to make thebest therapeutic utility of prostacyclin, particularly in the treatment of pulmonary arterialhypertension. This has centred on working out the detailed pharmacology of prostacyclin andthen synthesising new molecules based on its structure that are more stable or more easilytolerated. In addition, newer molecules have been developed that are not analogues ofprostacyclin but that target the receptors that prostacyclin activates. Prostacyclin and relateddrugs have without doubt revolutionised the treatment and management of pulmonary arterialhypertension but are seriously limited by side effects within the systemic circulation. Withthe dawn of nanomedicine and targeted drug or stem cell delivery systems it will, in the verynear future, be possible to make new formulations of prostacyclin that can evade the systemiccirculation allowing for safe delivery to the pulmonary vessels. In this way, the fulltherapeutic potential of prostacyclin can be realised opening the possibility that pulmonaryarterial hypertension will become, if not curable, a chronic manageable disease that is nolonger fatal. This review discusses these and other issues relating to prostacyclin and its usein pulmonary arterial hypertension.