In a total population survey of childhood psychosis in the region of Göteborg, 20 children (2 in every 10,000) fulfilled the diagnostic criteria for infantile autism formulated by Rutter. There was a male preponderance with 15 boys and 5 girls. Eighty-five percent of the mothers were older than average. Mean maternal age in the autistic sample was 30.7 years, compared with 26.0 years in the general population. The difference is statistically significant at the .1% level. There was a strong tendency toward increasing risk of autism in the child with increasing maternal age. The fathers too were much older than average.