The pupil dark response and maintenance of pupil area in darkness were compared in seven narcoleptic patients and 14 age-matched normal volunteers. Onset and degree of miosis after maximal pupil dilation in darkness were similar in the two groups, although three narcoleptic patients and no normal volunteers fell asleep during the experiment. The results of this study-contradict earlier suggestions that pupillography can be used to distinguish normal individuals in family studies of narcoleptic patients.