The most important component to the evaluation and treatment of hypertension is the accurate measurement of BP. Evaluation of BP in the office is limited by; small number of measurements, poor technique, the white coat effect (increase in BP in the medical environment) and the masked effect (a decrease in BP that happened in the medical environment). For these reasons there is considerable increased focus on out of office BP measurements. This includes the utilization of either home self-BP measurement or ambulatory blood pressure measurement (ABPM). Both techniques can accurately determine the presence of both white coat hypertension and masked hypertension. Increasing data suggests that out of office BP measurements by both measures give a better assessment of future cardiovascular risk than office BP. Finally the use of out of office BP monitoring has been associated with lower costs, and lower numbers of antihypertensive agents.