Interposed between the two sides of the heart and embedded within the matrix of the lung, the pulmonary circulation plays a pivotal role in the cardiopulmonary functions of gas exchange and oxygen transport. Its central position, however, renders the pulmonary circulation vulnerable to injury as a result of developmental or acquired disorders affecting the heart or lungs, as well as conditions that may also affect the systemic vasculature. Accordingly, pulmonary vascular disease is not the exclusive domain of any medical discipline: specialists in respiratory medicine, cardiology, rheumatology, infectious diseases, hematology, and pediatrics, among others, must all provide care for patients with these conditions. The most serious and potentially devastating chronic disorder of the pulmonary circulation is pulmonary hypertension (PH), a hemodynamic abnormality of diverse etiology and pathogenesis that challenges physicians with both its diagnosis and treatment. This document, developed by a multidisciplinary panel of experts, is intended to provide physicians with comprehensive, evidence-based guidelines for the approach to patients with pulmonary arterial hypertension (PAH).