Pulmonary arterial hypertension (PAH) is a progressive and fatal condition manifested by elevated pulmonary arterial pressure as a result of increased pulmonary vascular resistance. Clinical and therapeutic advances have improved survival and changed the course of the disease. However, clinical reversal and cure remain elusive, and much better understanding of this complicated disease process is needed to impact overall morbidity/mortality. This book of nine chapters by PAH experts provides an overview of the pathogenesis, clinical manifestations and approaches to treatment to help the reader to better understand the pathogenesis and management of the complicated disease.