Accurate measurement of arterial pressure is necessary for diagnosis of hypertension and for assessment of its therapy. The development and growing application of ambulatory blood pressure monitoring (ABPM) furthers these goals. Use of ABPM has defined white coat hypertension (WCH) and masked hypertension (MH), important prognostic diagnoses. ABPM categorizes blood pressure in several ways that increase accuracy for diagnosis and prediction of cardiovascular risk. Measurements of blood pressure throughout the day, at night during sleep, during the morning surge, and, in some instances selected intervals can be especially valuable for both research and clinical management. ABPM is being explored for its value in measuring pulse pressure and a derived index of arterial stiffness. ABPM has also shown to be valuable for defining the effects of antihypertensive drugs therapy. Results of such studies are crucial for advancing antihypertensive management. This review will summarize the important and emerging role of ABPM in defining risk for cardiovascular disease.