Aging is characterized, among many others, by changes in sleep-wake patterns, decrease in psychomotor activity during the day and decline in amplitude of melatonin, body temperature and cortisol (so-called circadian rhythm's markers). Epidemiologic data indicate that the prevalence of insomnia increases with age. Older individuals awake frequently during the night, have less slow-wave sleep, take day-time naps more frequently, go to sleep earlier with longer staying at bed and awake earlier. In this article, pharmacokinetic and pharmacodynamic properties of Circadin, a first prolonged-release formulation of melatonin which improves sleep quality, are described. In contrast to commonly used benzodiazepines, Circadin does not deteriorate cognitive skills during the day. It is suggested that Circadin may be helpful in withdrawal from hypnotic benzodiazepines.