Although narcolepsy is rarely diagnosed before adulthood, symptoms often begin much earlier and can easily mimic psychiatric disorders in children and adolescents. Clinical experience from a pediatric sleep center is reviewed in 16 consecutive cases of polysomnographically proven narcolepsy with onset of symptoms by age 13 years. Only 1 of the 16 patients presented with the classic clinical tetrad of symptoms (sleepiness, cataplexy, hypnagogic hallucinations, and sleep paralysis). Behavioral and emotional disturbances were present in 12 of 16 cases, with four patients appearing to have been misdiagnosed with a psychiatric disorder before recognition of the narcolepsy. Obesity appeared as an unexpected association in this case series, with 11 of the 16 narcoleptic patients found to be overweight at the time of diagnosis. The varied clinical presentations, polysomnographic findings, family history, and associated psychiatric symptoms are described. The importance of considering narcolepsy in the differential diagnosis of any child or adolescent with excessive sleepiness is emphasized.