Adolescents throughout the world do not obtain adequate sleep. A recent proliferation of experimental and quasi-experimental studies has considerably clarified the relationships between sleep loss and neurobehavioral function suggested by earlier epidemiological and cross-sectional studies. These new studies concur in finding that multiple successive nights of restricted sleep can impair multiple cognitive and affective functions. These effects cumulate from night to night, may not fully recover after weekend recovery sleep and may even be compounded by re-exposure to sleep restriction. An hour long afternoon nap reduces sleepiness in addition to improving vigilance, memory encoding and mood without interfering with nocturnal sleep when the latter is shortened. However, this does not detract from the point that adolescents require approximately 9 h of sleep per night for optimal neurobehavioral function, a message that more need to embrace.