Normal aging is accompanied by changes in the sleep quality, quantity, and architecture. Specifically, there appears to be a measurable decrease in the ability of the healthy elderly to initiate and maintain sleep, accompanied by a decrease in the proportion of the deeper, more restorative slow-wave sleep and rapid eye movement sleep. There is epidemiologic evidence that this impaired ability to initiate, maintain, and ultimately achieve good quality, optimal sleep may be a marker of increased mortality and neurocognitive dysfunction. Possible mechanisms related to these age-related changes in sleep include age-related changes in circadian modulation, homeostatic factors, cardiopulmonary function, and endocrine function. This article describes the normal changes in sleep physiology in the elderly.