Narcolepsy is characterized by irresistible daytime sleep episodes and cataplectic attacks. Because of the finding of an ultradian rhythmicity of slow-wave sleep in narcolepsy, an alteration of nonrapid eye movement sleep homeostatic regulation has been hypothesized to explain the impairment of the sleep-wakefulness cycle. This hypothesis was tested by two different methods: 1) a sleep-deprivation method (16 or 24 hours) increasing the prior sleep wakefulness and 2) a bed-rest method shortening the prior sleep wakefulness. In both studies normal subjects, sex- and age-matched to narcoleptic subjects, served as controls. Although some differences could be evidenced between the two groups, it was clearly shown that the homeostatic process was functional in narcolepsy and that narcoleptics seemed to be more sensitive to homeostatic regulation of sleep than normal subjects.