The circadian rhythms of blood pressure is regulated by various mechanisms, such as the autonomic nerve system, the renin-angiotensin system and hormones. Non-dippers are defined as those with a nighttime blood pressure reduction of less than 10% of daytime blood pressure. Many reports say that non-dippers have increased risk of cardiovascular or cerebrovascular disease. Ambulatory blood pressure monitoring (ABPM) is a useful tool for diagnostic and management of abnormal blood pressure variability in hypertensive individuals. Antihypertensive agents have the potential to provide blood pressure control of non-dipper patients. 24-hour blood pressure control with ABPM may be necessary for patients to get better prognosis by blood pressure lowering therapy.