Studies have confirmed that the endothelin pathway plays an important role in the pathogenesis of pulmonary arterial hypertension. The dual endothelin receptor antagonist, bosentan, prevents or even reverses pulmonary vascular remodeling and right ventricular hypertrophy by blocking ETA and ETB receptors, decreasing right ventricular afterload and thereby improving patients’ clinical symptoms and exercise tolerance. From 1993, when bosentan was first developed, to the present, endothelin receptor antagonists have the best evidence-based medicine for the treatment of pulmonary hypertension. In 2002, Rubin et al. reported the results of the BREATHE-1 study, in which 213 patients with WHO functional class III or IV primary pulmonary hypertension and scleroderma-related pulmonary hypertension were enrolled and treated with bosentan and placebo, respectively. The mean increase in 6-minute walking distance was 36 meters in the bosentan group at 16 weeks of the study compared to a mean decrease of 8 meters in the placebo group; clinical deterioration was found to be significantly later in the bosentan group than in the placebo group at 28 weeks of the study. In 2005, McLaughlin followed 169 patients with primary pulmonary hypertension who had been treated with bosentan as first-line therapy for more than 3 years and found survival rates of 96% and 89% at 12 and 24 months of bosentan treatment, respectively, compared to 69% and 57% predicted by the NIH survival formula. This study demonstrates that bosentan is a medically evidence-based agent that has been shown to improve long-term prognosis. In 2006 Galiè et al. published the results of the BREATHE-5 study, which enrolled 44 patients with WHO class III cardiac function Eisenmenger syndrome. Compared to the placebo group, the bosentan group showed a decrease in pulmonary vascular resistance of 472.0 dyn ? s ? cm-5, a 5.5 mm Hg decrease in mean right atrial pressure, and a 53.1 m increase in 6-minute walking distance. This study demonstrated that bosentan consistently improves quality of life in patients with Eisenmenger syndrome and is a novel and effective drug for the treatment of Eisenmenger syndrome. In 2003, Barst et al. applied bosentan to the treatment of children with pulmonary hypertension (BREATHE-3 study). 19 children with pulmonary hypertension showed a decrease in mean pulmonary artery pressure of 8.0 mmHg and a decrease in pulmonary vascular resistance of 300 dyn ? s ? cm-5, which was well tolerated in all groups. This study is the first to demonstrate that bosentan has similar pharmacokinetics in children with pulmonary hypertension and adults with pulmonary hypertension, and that it can significantly improve hemodynamics and be safely used in the treatment of pulmonary hypertension in children. In 2005, the results of a single-center, open study of bosentan for inoperable chronic thromboembolic pulmonary hypertension (CTEPH) were reported, showing improvements in 6-minute walk distance, cardiac function class, serum markers and hemodynamic parameters after 3-6 months of bosentan treatment. Bosentan significantly improved exercise tolerance, hemodynamic parameters and survival in chronic thromboembolic pulmonary hypertension. With the publication of new clinical studies, the use of endothelin receptor antagonists has expanded from the initial use in idiopathic, connective tissue disease-associated and congenital heart disease-associated pulmonary hypertension to include HIV infection-associated pulmonary hypertension, chronic thromboembolic pulmonary hypertension and pulmonary hypertension in children. The results of a multicenter study of bosentan for pulmonary hypertension in China also confirmed the definite efficacy of bosentan in pulmonary hypertension in China .