Many aspects of cardiovascular physiology are subject to diurnal variation, and serious adverse cardiovascular events, including myocardial infarction, sudden cardiac death, and stroke, occur with a frequency conditioned by the time of day. Over the last decades, growing evidence has revealed the existence of an endogenous oscillator intrinsic to the cell—called the molecular clock—that orchestrates the physiology of such time-dependent oscillatory patterns of events. In the present review, we first provide a short overview of the molecular basis of the oscillator. Then, we explain the organization of the clock at the level of the organism. We discuss the current understanding of the role of clocks in cardiovascular physiology and summarize potential entraining signals of relevance to cardiovascular function. Finally, we consider the interaction between the clock and metabolic function, which can also impinge on the propensity to cardiovascular disease...