Pulmonary hypertension is a complex and multidisciplinary disorder. The classification of pulmonary hypertension includes 5 groups. Pulmonary arterial hypertension is a rare disorder that can be idiopathic or heritable in nature, or associated with other conditions, such as scleroderma or congenital heart disease. The recent decades have realized advances in the treatment of this once devastating disease. More commonly, pulmonary hypertension is associated with other disorders, such as those that elevate left heart filling pressures and hypoxemic lung disease. Chronic thromboembolic disease can result in pulmonary hypertension. To determine the etiology, a thorough and methodical evaluation must be completed. Often, an echocardiogram is the first test to suggest the diagnosis of pulmonary hypertension. Studies to identify potential associated causes are important. The diagnostic evaluation culminates in right heart catheterization. Over recent years, advances in therapies, including the prostacyclins, the endothelin receptor antagonists, and the phosphodiesterase type 5 inhibitors, have resulted in an improved quality of life and outlook for patients with what is often a progressive disease.