The authors observed the syndrome in a 17-year-old boy weighing 86 kg and training weight-lifting. During between 10 and 20 months he had periods of physiological sleep lasting on the average 7 days, with voracious appetite and dysphoris. In the EEG tracings corresponding to physiological sleep were observed during the somnolence period, later in transient changes appeared, mainly in the forebrain. EDP in the cerebrospinal fluid was raised - 0.4 micrograms/ml (normally 0--0,05 micrograms/ml according to Merskey). The results of other laboratory investigations were normal. Since about 3 months the patient has been completely healthy and his scholastic progress in good. The authors suspect that excessive exertion may be a causative factor in this syndrome when it occurs at the time of adolescence.