To investigate the effectiveness of "nap therapy" for improving alertness and reducing the frequency of sleep attacks, 16 narcoleptic subjects were studied before, during, and after a 1-month program of three regularly scheduled naps. The frequency and timing of sleep attacks, naps, and nocturnal sleep periods were recorded daily in sleep logs for 5 weeks. The severity of five common symptoms of narcolepsy and daytime alertness were assessed before and after the 1-month treatment period. Medications and usual nocturnal sleep habits were not changed during the study period. Mean sleep latency was increased significantly after 1 month of nap therapy. However, there were no significant changes in the frequency of sleep attacks or in the severity of other symptoms. Those subjects who reported more severe symptoms and who had taken more naps daily before the study period received the most benefit from the treatment.