Narcolepsy is a potentially invalidating disorder of the sleep and wakefulness structure, characterized by attacks of sleepiness, cataplexy, hypnagogic hallucinations, sleep paralysis and disturbed night sleep. The diagnosis is mainly based on the history. Additional sophisticated examinations, such as nocturnal polysomnography, are primarily indicated to rule out other causes of excessive daytime somnolence. The recently detected high correlation between a certain HLA status and cataplexy has led to new pathogenetic concepts. The primary aim of the therapy is to keep the patient at work rather than attempting a symptom free state. Measures to organize his day with planned naps should precede the use of medication. Besides stimulants against daytime somnolence and tricyclic antidepressants to suppress cataplectic attacks, some new drugs have been administered successfully against the various symptoms of narcolepsy in recent years.