Insomnia is not only the most common sleep disorder in the population, it is a frequent complaint heard overall by primary care physicians and specialists alike. Given the high prevalence of this disorder, its tendency to persist, and the frequency with which patients complain of symptoms in practice, it is imperative to have an understanding of basic sleep-wake mechanisms and the evolving field of pharmacologic approaches to enhance sleep. Currently, pharmacologic approaches are among the most widely used therapies for insomnia. This article reviews sleep-wake mechanisms, the neuroanatomic targets for sleep and wake-promoting agents, and discusses currently used agents to promote sleep and investigational hypnotics.