The exact cause and physiological limits of blood pressure (BP) delineating hypertension are not known. Hence, controversies remain regarding the diagnosis and drug therapy. The new ACC/AHA 2017 Guidelines for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults have several limitations and do not give much consideration to ambulatory blood pressure (BP) monitoring (ABPM) or to the chronobiologic interpretation of the data, including an assessment of circadian patterns or the significance of BP during sleep. Most recommendations support a more aggressive diagnostic and treatment approach, consistent with growing evidence from clinical trials and epidemiological studies that do not rely on ambulatory monitoring of BP. In view of the newly proposed lower limits, the challenge is how clinicians will translate these guidelines into clinical practice without over-diagnosing hypertension and making sure appropriate treatment is prescribed in the absence of information derived from ABPM. Disregarding circadian BP patterns and BP values during sleep is likely to lead to a high proportion of misdiagnoses. The new guidelines emphasize home BP measurements rather than ABPM. Whereas the longitudinal aspect gained by home BP has great value, it cannot replace the information about circadian variation in BP provided by ABPM, which requires reliable measurements during sleep. In view of the large day-to-day variability in BP, and since abnormal BP variability carries a non-negligible cardiovascular disease risk, even in normotensive individuals, the Halberg Chronobiology Center (HCC) has long advocated the use of ABPM for at least 7 days in all adults, regardless of whether office BP is normal or elevated, in order to accurately assess cardiovascular risk. The International Society of Chronobiology (ISC) has also proposed that the asleep systolic (S) BP mean can serve as an independent predictor of adverse cardiovascular events. The drop in SBP during sleep adds prognostic value to the statistical model that already includes the asleep systolic BP mean, accounting for relevant confounding variables. The Indian Society of Chronobiology fully endorses the recommendations made by the HCC and ISC and propose to rely on 7-day/24-hour ABPM, interpreted chrono-biologically for the diagnosis of hypertension and other “vascular variability disorders” (abnormal circadian patterns of BP and heart rate), and as a guide for the optimization of treatment by timing (chronotherapy). © 2018 Nova Science Publishers, Inc.