This epidemiological study of autistic children was carried out in Yogyakarta, Indonesia. The approaches considered included the analysis of cross-sectional data on non-verbal intelligence, social maturity behavior or adaptive skills test by using statistical or sampling controls. The 5,120 children studied were all Javanese. Doctors, nurses of Public Health Centers and school teachers assisted in assessing the above subjects. The Bryson's screening scale for evaluating autistic children was used. A total of 66 children who scored above 16 were identified. Final diagnosis was done by means of CARS. Six children, who lived within Yogyakarta Municipality, were identified. The prevalence rate of autism within the birth cohort who were born between June 1984 and May 1991 was 12 per 10,000. Observations of the social interactions of 6 autistic and 6 normal children of equivalent mental age were carried out during a free play situation and reunion situation with mother and a stranger. A comparison of the two groups during social interaction made it clear that the autistic children showed more attachment, directed more social-interaction and more physical contact toward their mothers than to strangers during the reunion situation.