This is a report of physiological, psychological and psychopathological studies of eight cases of narcolepsy. No evidence for an epileptic basis for the narcoleptic seizures was obtained. The evidence for excessive 'vagotonia' was doubtful. Personality studies suggested some common traits of narcissism, passivity and dependence on mother. To study narcolepsy as a disorder of vigilance would be a step in elucidating its real pathophysiology.