Twenty seven patients with parasomnias (night terrors, nocturnal motor automatisms, nocturnal verbal automatisms and sometimes with bruxisms) associated with magnesium deficiency were selected. In all of them marked hypomagnesemia, clinical, EEG and EMG signs of spasmophilic syndromes were found. The 8 hours polysomnographical recordings of all cases (monitored in a system with infra-red video-TV cameras) showed severe sleep disorders and EEG nocturnal abnormalities occurring in the SWS (especially in the I b, II and III stages) with disappearance in the REM sleep. The authors suggest that these clinical and polysomnographic anomalies may be the expression of the brain damage caused by magnesium deficiency or of the clinical electrographic manifestations of the reticulate neuronal hypersynchrony exacerbated by sleep.