This study was designed to test the safety and efficacy of pulmonary artery (PA) denervation (PADN) for patients with idiopathic PA hypertension (IPAH) not responding optimally to medical therapy. Baroreceptors and sympathetic nerve fibers are localized in or near the bifurcation area of the main PA. We previously demonstrated that PADN completely abolished the experimentally elevated PA pressure responses to occlusion of the left interlobar PA. We report for the first time the effect of PADN on functional capacity and hemodynamics in patients with IPAH not responding optimally to medical therapy. Further randomized study is required to confirm the efficacy of PADN. (First-in-Man Pulmonary Artery Denervation for Treatment of Pulmonary Artery Hypertension [PADN-1] study; chiCTR-ONC-12002085) (J Am Coll Cardiol 2013;62:1092–100) a 2013 by the American College of Cardiology Foundation