Body movements during sleep were observed in 14 full-term sick newborn infants such as perinatal asphyxia, purulent meningitis, meconium aspiration syndrome, melena, porencephaly, and hydranencephaly. Five newborn infants who had recovered from transient vomiting were examined as control. Infants with minimally depressed background EEG showed an increase of generalized movement (GM) and localized tonic movement (LTM) in quiet sleep. Hydranencephalic infants revealed an increase of generalized phasic movement (GPM) in active and quiet sleep. On the other hand, a decrease or an absence of body movements was observed in infants with severe EEG abnormalities such as moderate, marked and maximal depression. Hydranencephalic and porencephalic neonates showed a decrease of LTM in active sleep. One infant with purulent meningitis, showing markedly depressed EEG, revealed GPM-like movements of much longer duration. The follow-up study revealed that the absence of body movements or the increase of GPM might indicate a very poor outcome, whereas the presence of LTM, even in a small amount, suggested the preservation of cortical functions. The increase of body movements was also considered to correlate with sleep disturbance and served to indicate a brain dysfunction.