Vigilance, memory function, and response latency on the Sternberg short-term memory scanning task were examined in eight narcoleptic patients on and off medication. Off medication, half of the patients demonstrated reduced vigilance and all displayed diminished automatic memory encoding and longer response latencies on the Sternberg memory scanning procedure relative to the treated condition. Protriptyline normalized vigilance in half of the patients, while response latency and automatic information processing significantly improved in all. These findings are discussed with regard to the potential effect of the medication on central nervous system arousal.