The prenatal and neonatal factors of 225 children diagnosed with Autistic Disorder were compared with those of 1580 typically developing children. Each of the neonatal factors was compared between the Autistic Disorder and control groups, and between males and females. The results showed that males in the "Autistic Disorder" group had a significantly longer gestational age and a heavier birth weight than the male controls. No significant differences in these factors were observed between females in the two groups. Both male and female children with Autistic Disorder showed a significantly higher incidence of neonatal complications than their respective controls. In the Autistic Disorder group, males had a heavier mean birth weight, and there were more post-term infants among females.