For the purpose of clarifying the pathophysiological meaning of sleep disturbance in autistic children, the sleep pattern of 75 such children was examined by a questionnaire method. Forty-nine of them showed sleep disturbance in their early life with an incidence of 65%. The poorly-developed group showed a high rate of sleep disturbance as compared with the relatively well-developed group. There was a negative correlation between the developmental level and duration period of sleep disturbance. The investigation of circumstances in which autistic children often exhibited sleep disturbance proved that abrupt changes in life environment or various problems in the way of bringing up children brought about their sleep disturbance. These findings suggest that sleep disturbance might be one of the main symptoms and related to the pathophysiology of infantile autism.