Unfavourable pre-, peri- and neonatal events in the birth records of autistic children were examined. The rate of those factors was compared with the expected rate in the general population and the rate in their non-autistic siblings. Several potentially neuropathogenic factors occurred at a significantly high rate in the autistic group, including breech delivery, the presence of amniotic meconium, low birth weight, low Apgar score, elevated serum bilirubin, haemolytic disease and Respiratory Distress Syndrome. The autistic children had significantly more unfavourable factors than did their siblings. The study supports the findings of investigations which concluded that autistic children have suffered a high rate of obstetrical events which may have caused brain damage.