As the leading risk factor in cardiovascular disease, the management and treatment of hypertension has been at the forefront in primary care preventive medicine. Oftentimes, a mean blood pressure measurement obtained in a clinic setting has been used as the most important therapeutic metric in making management decisions; this may lead to an overly simplistic and erroneous conclusions due to variations during the day and night. Thus, due to oscillations during the day, measurement of a single clinic-based blood pressure is an inconsistent metric for a definable goal and therefore has often been problematic in hypertension monitoring. Dr. Erum Malik and his colleagues from the Department of Medicine at Einstein Medical Center (Philadelphia, PA) and Advocate Christ Medical Center (Oak Lawn, IL) give a comprehensive overview on blood pressure variations and its clinical consequences. Editor-in-Chief Jerrold B. Leikin, MD