This issue of JAMA, from illustrated cover to in-depth content, is dedicated to hypertension, a worldwide problem of enormous consequence. High blood pressure affects more than 1 billion people worldwide, and that number is increasing. Untreated or uncontrolled, hypertension is the single largest contributor to cardiovascular disease, causing stroke, heart failure, and coronary artery disease, and also is a major contributor to kidney disease. Progress over the last several decades has led to increased understanding of the relationship between blood pressure and health outcomes and to the development of multiple antihypertensive therapies that reduce the risk. New knowledge carries with it a mandate to address the growing global epidemic of hypertension.