The impact of sildenafil on pulmonary arterial hypertension (PAH) in Chinese patients has been less investigated. A prospective, open-label, uncontrolled and multicenter study, therefore, was carried out to address this issue. Ninety patients with multicause-induced PAH received oral sildenafil (75 mg/day) for 12 weeks. The 6-minute walk test (SMWT) and cardiac catheterization were performed at the beginning and the end of the 12 weeks. The primary endpoint was the changes in exercise capacity assessed by the SMWT; the secondary endpoint included assessment of functional class, evaluation of cardiopulmonary hemodynamics, and clinical worsening. Drug safety and tolerability were also examined. The results showed that there was a significant improvement in SMWT distances (342 ± 93 m vs 403 ± 88 m, P <.0001), Borg dyspnea score (2.9 ± 2.6 vs 2.4 ± 2.0, P =.0046), World Health Organization functional class, and cardiopulmonary hemodynamics (mean pulmonary artery pressure, P <.0001; cardiac index, P <.0001; pulmonary vascular resistance, P <.0001) after 12 weeks of oral sidenafil therapy. Almost all enrolled patients did not experience significant clinical worsening. This study confirms and extends the findings of previous studies relating to effects of sildenafil on PAH, suggesting that oral sildenafil is safe and effective for the treatment of adult patients with PAH in the Chinese population. © 2012 American College of Clinical Pharmacology, Inc.