Ambulatory Blood Pressure Monitoring (ABPM) is considered the best method for obtaining a reliable estimation of the true blood pressure. Average values obtained during the whole 24-hour period, or during daytime and nighttime periods are better correlated with the risk of mortality and cardiovascular disease compared to clinic or office blood pressure. Indeed, nighttime blood pressure, a measure only obtained through ABPM, is the most powerful risk predictor. ABPM is complementary to clinic blood pressure measurement and allows the definition of blood pressure phenotypes, such as "white-coat or masked hypertension, when clinic and ABPM measurements show discrepancy in normal values. Additional potentially relevant features include blood pressure variability, such as nocturnal blood pressure decline, morning surge or short-term variability, as determined by standard deviation or the coefficient of variation.