Narcolepsy is well known disease from many years. Its diagnosis in Poland is rarely in the contrary to western countries or United States where its frequency is estimated from 5 to 10 cases per 10 000 people. Narcolepsy is characterised by excessive and repetitive daytime sleepiness, catalepsy, sleep paralysis and hypnagogic hallucinations. In healthy people the sleep is beginning from non-REM phases, but in the narcoleptic patients is immediately beginning from the REM phase of sleep. The association of narcolepsy with HLA DR2 and recently with HLA DQB1*0602 has been found. In humans, the hypocretin deficiency in the cerebrospinal fluid and a loss of the hypocretin neurons in the brain hypothalamus post mortem has been found. The prostaglandin D2 takes part in the process of sleep, which are synthetised in the human brain by the synthetase of prostaglandins. Many years ago in the treatment of narcolepsy were used amphetamine or ephedrine. Broughton et al. in 1988 year start with modafinil in the treatment of narcolepsy with very good results. Recently were trials of narcolepsy with GABA derivates, for example Xyrem, unfortunately this drug posses very dangerous side effect. The catalepsy was treated with tricyclic antidepressants, for example imipramine, clomipramine, amitryptiline or fluoxetine.