We surveyed the prevalence of infantile autism in Kurume City. Children born between 1971 and 1979 ranged in age from 4 to 12 years at the time of the survey. We found 51 cases of infantile autism. In each year group, we determined the ratio of the number of cases of infantile autism to the total number of children. The prevalence ranged from 10.4/10,000 to 17.5/10,000, with a mean prevalence of 15.5/10,000. The sex distribution was 42 males (prevalence of 24.8/10,000) and nine females (prevalence of 5.7/10,000). The results showed a significant sex difference, with a male:female ratio of 4:1 (p less than 0.0005). High prevalence rates of infantile autism in Kurume City were confirmed.