Pulmonary arterial hypertension (PAH) is characterized by the progressive increase in pulmonary vascular resistance potentially leading to right heart failure and death. Since endothelins may play a pathogenic role in the development of the disease, endothelin receptor antagonists have been proposed for the treatment of this condition. Bosentan (Tracleer), an oral nonselective ET(A)/ET(B) endothelin receptor antagonist, has been shown to improve exercise capacity, quality of life and hemodynamics of patients with PAH in short-term trials. These improvements were sustained and a long-term observational study on idiopathic PAH patients suggested a favorable effect on survival in this subset. The present report summarizes the pharmacology, clinical efficacy and safety profile of bosentan with an overview of the current therapies available for the treatment of PAH.