From a population-based series of children with Infantile Hydrocephalus (IH) 69 patients (mean age 11.7 years) were examined with respect to the occurrence of autistic symptoms. Autistic symptomatology was evaluated according to a modified short Swedish version of the so-called Autism Behavior Checklist. Sixteen of the 69 IH children (23%) reached a score which was considered indicative of autistic symptoms (AS) in the child. This group was compared with the remaining 53 IH children without autistic symptoms (non AS). Significant differences were found between these two groups with respect to aetiological and clinical data. In the AS group 44% were born preterm as compared to 9% in the non AS group. CT scan showed major abnormalities in 64% of the AS children while this was present in 28% in the non AS group. The occurrence of major neuroimpairments--epilepsy, mental retardation and cerebral palsy--was 50%, 88% and 50% in the AS group as compared to 9%, 23% and 19% respectively in the non AS group. It was concluded that the more severe the brain damage in children with IH the more likely that autistic symptomatology would ensue. This implies that specific neuropsychiatric services to these families are required.