Two patients (females aged 13 and 45)suffering from recurrent hypersomnia were examined by polysomnography in the symptomatic period;the younger patient underwent polysomnography also in the asymptomatic period.The sleep in the symptomatic period of these patients had no common features except fragmentation and stage 1 and 2 NREM prolongation.Both patients were somnolent and apathetic during wakefulness and the older patient also agitated.The 13-year-old subject did not eat more during the symptomatic period but she gained 3 kg each time.The 45-year-old patient overate several days after the period of sleep.No abnormal sexual behaviour was referred.The symptomatic periods occurred in the 45-year-old patient during menstruation.Therapy by lithium alleviated the symptoms in both patients.

        Key words: recurrent hypersomnia,Kleine-Levin syndrome,hypersomnia,polysomnography,lithium