Kleine-Levin syndrome is a rare self-limited disorder which usually affects adolescent males and is characterized by episodic hypersomnia, increased appetite, and behavioral/psychiatric disturbances. Individuals are normal between the attacks. The case of an adolescent boy is presented who suffered from recurrent sleepiness, hyperphagia, and behavioral disturbances such as rocking, punching and pacing, and was originally misdiagnosed as suffering from encephalitis. Before the diagnosis of Kleine-Levin was given, the patient underwent unnecessary investigations and treatment which, in turn, complicated his clinical condition both physically as well as psychologically. In the course of five years he had four such episodes which appeared to have progressively milder manifestations. Between episodes he was normal. It is important that the diagnosis is suspected early, especially in adolescent males who present with recurrent episodes of somnolence, increased appetite, and abnormal behavior, since it most often represents a benign and self-limited entity and does not warrant extensive investigations or treatment. It is also important to distinguish this syndrome from more serious organic and psychiatric diseases with more serious prognoses. The differential diagnosis of this syndrome is discussed and a review of the literature is presented including evidence and hypotheses regarding its pathophysiology.