Accumulating evidence suggests that the molecular circadian clock acts as a master regulator of gene expression in the kidney. The core clock genes, including Bmal1, Period 1, Clock, and Cryptochrome 2, all exhibit circadian expression in the mouse kidney (Figure). Global transcriptomic approaches have revealed the important finding that there are thousands of genes in the kidney subject to regulation by the molecular clock [1][2]. One example is that the circadian clock protein Per1 transcriptionally regulates the alpha subunit of the epithelial sodium channel (αENaC)[3]. Candidate gene approaches have also yielded information regarding regulation of renal sodium transport genes by the molecular clock [4].To date, the evidence linking the molecular kidney clock to rhythmic renal function provides strong support for the concept that circadian control of gene expression underlies rhythms in physiological function. In this presentation, an overview of the molecular and physiological evidence for the kidney clock and the implications for the regulation of renal physiology and pathophysiology will be presented.