The circadian blood pressure (BP) rhythm is associated with worsened cardiovascular outcomes in patients who have an excessive morning BP surge and in those who lack the normal nocturnal BP fall (non-dippers). There are multiple pathophysiologic mechanisms underlying abnormalities in circadian BP, most importantly abnormalities in sympathetic nervous system activity, salt and volume balance, and activation of the renin-angiotensin system. Several of these factors can be modified by clinical interventions, either related to lifestyle changes and/or antihypertensive drug therapy. The timing of drug administration or specific drug delivery systems that lead to a greater effect at night and/or mitigate the early morning BP surge can correct abnormal circadian rhythms. Although these strategies have not yet been shown to alter clinical outcomes, it is reasonable to understand their biologic basis and take them into consideration when designing antihypertensive therapy.