The etiology of schizophrenia in children under five (early infantile autism) appears just as obscure and as varied as the etiology of adult schizophrenia. In reference to an older age group, 5-15, Kallman6 suggested that the genetics of childhood schizophrenia were identical to the genetics of the adult variety. In short, he suggested that nearly all identical twins were concordant for the disorder, that a much smaller but significant number of heterozygous twins should be affected, and that the percentage of affected heterozygous twins should be roughly equal to the percentage of affected siblings. Kanner,9 on the other hand, suggested that schizophrenic heredity plays a negligible role in the disorder; he found only three out of 131 siblings of autistic children were themselves autistic.
The following case history of 11-year-old heterozygous twins discordant for early infantile autism is offered as a well-documented clinical situation where environmental