Narcolepsy-cataplexy syndrome is characterized by irresistible daytime sleepiness, an abrupt decrease in muscle tone aroused by emotion, sleep paralysis, and hypnagogic hallucinations. This rare syndrome mostly affects males and is usually seen in the second decade. A complex interaction of environmental and genetic factors has been implicated in the etiology; also a close relationship has been demonstrated with some HLA subgroups (HLA DQB1*0602, HLA DR2). Moreover, several studies documented an association with hypocretin deficiency. Clinical findings and polygraphic sleep recordings (nocturnal polysomnogram, multiple sleep latency test) are important in the diagnosis. Central nervous system stimulants such as amphetamine and methylphenidate and somnolytic agents such as modafinil are used in the treatment of narcolepsy, while cataplexy is treated with antidepressants.