ABSTRACT Narcolepsy is a chronic neurological disease characterized by diurnal excessive sleepiness and catapleaxy. It affects 1 in every 2000 to 4000 individuals with personal, social and familiar significant repercussions. The treatment of narcolepsy is mainly based on the use of stimulants for the control of the diurnal excessive sleepiness, in conjunction with behavioral measures and sleep hygiene. Among the stimulants, modafinil has presently been the drug of choice for the treatment of the diurnal excessive sleepiness in patients with narcolepsy. In the worldwide experience, its use is better tolerated and the majority of its side effects is considered light or moderate. However, the clinical use in Brazil was initiated at the end of 2008, with little experience on the narcolepsy population of this country. In this context, the objective of this study was the evaluation of the use of modafinil, verifying the indication of use, causes for discontinuation, daily dosage, efficiency of the treatment in a patient sample of narcoleptics consulted in a specialized center in Brazil. In this study, modafinil was effective for the control of the symptoms related do narcolepsy in 66% of the studied patients. The side effects such as headache, parestesias and diarrhea were the main reasons for the discontinuation of treatment with modafinil. It is important to clinically follow up the patients for a long period to evaluate symptomatology, control of use, tolerability and re-evaluation of the more effective therapeutic dosage able to control narcolepsy. Due to its high cost and clinical benefits, this drug should be on the government's list of free drugs for the treatment of these patients.