Twenty-eight patients with narcolepsy are compared to a sex- and age-matched control population with regard to the frequency of psychiatric symptoms. The occurrence of psychiatric syndromes in narcolepsy patients is also examined. The frequency of psychiatric illness in patients with cataplexy or hypnagogic/hypnopompic hallucinations is evaluated as well. Analysis with the Mann-Whitney test found a significant association between narcolepsy and the symptoms of schizophrenia. Premorbid history of organic brain disease was associated with mental illness, but was nonspecific for psychopathology.