Previous studies have linked the mysterious and inevitable process of aging to essential processes such as metabolism, maturation, and fecundity. Each of these processes is controlled to a large extent by nuclear hormone receptors (NHRs). NHRs also play important roles in the control of periodical processes, the most recently implicated being circadian rhythm. This Review stresses the mounting evidence for tight relationships between each of these NHR-regulated processes and the processes of aging.