Book excerpt: Sleep is not only a biological necessity but also a physiological drive. In today's fast-paced world, though, a good night's sleep is often the first thing to go. The effects of inadequate sleep are more than mere annoyances: they affect our mood and how we perform at school, work, and home and behind the wheel. Lost sleep also accumulates over time; the more "sleep debt" an individual incurs, the greater the negative consequences, according to researchers in the field. Research on adolescents and sleep has been under way for more than two decades, and there is growing evidence that adolescents are developmentally vulnerable to sleep difficulties. To discuss current research in this area and its implications in the policy, public, health, and educational arenas, the Forum on Adolescence of the Board on Children, Youth, and Families held a workshop, entitled Sleep Needs, Patterns, and Difficulties of Adolescents, on September 22, 1999.