KLeine-Levin Syndrome (KLS) is a rare disease characterized by recurrent episodes of hypersomnia associated with cognitive and behavioral disturbances, compulsive eating behavior and hypersexuality. Episodes are separated by weeks or months of normal sleep and behavior. The disease predominantly affects adolescent males. The median duration of the disease is eight years. Fifteen percent of the KLS population is of Jewish origin and the incidence reported in Israel is unproportionately high. The etiology and pathophysiology are unknown. The current concept is that the disease is caused by genetic predisposition combined with environmental factors. Autoimmune etiology has also been suggested. KLS poses diagnostic and therapeutic challenges. Diagnosis is usually based on clinical manifestations. Physical examination including neurological evaluation is usually normal. EEG, brain imaging and CSF examination are normal. Stimulants are partially effective on sleepiness. Lithium was reported to induce positive effects in preventing or delaying recurrences. Increased awareness to KLS among physicians in Israel is important due to the relatively higher incidence of KLS among Jewish and IsraeLi patients.