Twenty 2- to 13-year-old infantile autistic children (16 boys and four girls) and four 4- to 13-year-old children (two boys and two girls) with other kinds of childhood psychoses were compared with eight 6-month-old to 6-year-old normal children with regard to cerebrospinal fluid contents of endorphin fractions I and II. The psychosis groups showed higher mean cerebrospinal fluid endorphin fraction II levels, and 11 (55%) of the 20 autistic patients showed values higher than the highest in the group of normal children. There was a trend toward a correlation between high fraction II levels and self-destructiveness and decreased pain sensibility in the psychotic children. The results are regarded as preliminary but as warranting further research in this potentially fruitful field.