Kleine-Levin syndrome is more commonly known as recurrent primary hypersomnia. The patient can lapse into a deep sleep at any time without warning, sometimes lasting as long as 16 hours. It is often associated with compulsive overeating and hypersexuality—this is not a passing desire for a quick nap, but is excessive daytime sleepiness, which is a much more significant problem. On awakening the person appears listless, speaks gibberish, and does not remember anything about events before falling asleep (short-term retrograde amnesia). We discuss the presentation, course of illness, pathophysiology, laboratory investigations, diagnosis, possible treatments, and the importance of early recognition of this disorder.