In older persons, sleep complaints in the form of insomnia and daytime drowsiness are highly prevalent and are associated with adverse outcomes. The underlying mechanisms are linked to age-related declines in physiology (normal aging) and age-related increases in disease prevalence (usual aging). This article describes how normal aging leads to less-restorative sleep, characterized by reductions in homeostatic and circadian sleep, and to phase advancement of the sleep-wake cycle, characterized by older persons being more alert in the early morning but drowsier in the early evening. It also describes how usual aging leads to sleep complaints through reductions in health status, loss of physical function, and primary sleep disorders. Psychosocial influences are likewise described, and their relevance to sleep complaints is discussed. These aging-related changes are subsequently incorporated into a conceptual model that describes sleep complaints as a consequence of multiple and interdependent predisposing, precipitating, and perpetuating factors, akin to a geriatric syndrome. The discussion concludes by applying the conceptual model to the sleep-related care of an older person with insomnia and daytime drowsiness and suggesting that the diagnostic assessment consider, in addition to primary sleep disorders, multiple domains, including medical, physical, cognitive, psychological, and social matters, with the intent of developing an overall therapeutic plan and establishing long-term follow-up.