Circadian rhythmicity affects all living organisms on earth. Central and peripheral cellular clocks have the ability to oscillate and be entrained to environmental cues, thus allowing organisms to anticipate and synchronize their physiologic processes and behavior to recurring daily environmental alterations. Disruption of the circadian rhythm in modern life, such as by shift work and jet travel, leads to dyssynchrony of the central and peripheral clocks, and is an independent risk factor for cardiovascular disease and the metabolic syndrome. Aging has also been associated with attenuated cellular rhythmicity. Here we summarize the clinical observations linking cardiovascular health to circadian rhythm. In addition, we discuss recent advances in experimental models for understanding the clock machinery in terms of a variety of physiologic processes within the cardiovascular system. Together, these studies build the foundation for applying our knowledge of circadian biology to the development of novel therapy for cardiovascular disorders.