Pulmonary artery hypertension occurs when there is a sustained elevation of the mean pulmonary pressure above normal physiologic values. This may then lead to cor pulmonale or enlargement of the right ventricle due to any lung disease in the absence of left heart failure. When the ability of the right ventricle to compensate is overwhelmed, right-sided heart failure can occur. Pulmonary artery hypertension may be idiopathic (primary) or secondary to a variety of lung parenchymal diseases, airways disease, pulmonary circulatory disorders, systemic illnesses, or thoracic mechanical abnormalities. Treatment strategies for cor pulmonale include supplemental oxygen, assisted mechanical ventilation, digoxin, and diuretics. Pulmonary vasodilator compounds should be used with caution because they can compromise gas exchange in cor pulmonale from secondary pulmonary hypertension. Trials with digoxin and inotropic agents have been evaluated. Angiotensin-converting enzyme inhibitors have not shown significant utility, at least acutely. Anticoagulation may decrease mortality in some patients with pulmonary artery hypertension and cor pulmonale.