This chapter presents the clinical history, examination, follow-up, treatment, diagnosis, and the results of the procedures performed on a 25-year old patient who was admitted for the evaluation of insomnia. The specialist made a diagnosis of narcolepsy with possible cataplexy and decided not to pursue a CSF hypocretin analysis in light of the diagnostic certainty of the polysomnography (PSG) results. The multiple sleep latency test (MSLT) showed the presence of REM sleep in all four naps with a latency of 5 minutes. He prescribed modafinil 200 mg to be taken in the morning, a dose that could be increased to 400 mg if necessary. Narcolepsy is a life-long disorder presenting with excessive daytime sleepiness (EDS) and, ironically, with fragmented sleep that may lead to an erroneous diagnosis of insomnia. In addition to modafinil, patients may respond favorably to the administration of methylphenidate and dexedrine.