A polygraphic investigation was made of daytime sleep in healthy infants with analysis of the EEG, oculogram, muscle tone, fluctuations in skin resistance, respiration, ECG, rheoencephalogram, and rheogram of the leg. Infants with cerebral palsy of perinatal genesis were investigated by the same method. The results showed that in early infancy it is possible to distinguish the basic stages of slow sleep and the stage of fast sleep, although the electroencephalographic experssion of these stages in infants has special features of its own. The age dynamics of the polygraphic picture of sleep shows that the electroencephalographic, autonomic, and motor components of sleep, although clearly coordinated in the various stages, have at the same time considerable autonomy. This is confirmed by the results obtained by analysis of the cerebral pathology. The need for adequate assessment of this complex function in order to elucidate the physiological nature of sleep is emphasized.