The somatomedins are a family of multitarget, growth-promoting hormones suggested to play a regulatory role in the central nervous system. Serum concentrations of somatomedins were determined by a radioreceptor assay in 26 patients (19 boys and 7 girls) with minor neurodevelopmental disorders. Five of these 26 patients showed high serum levels (greater than 2 S.D.) of somatomedins. It is concluded that patients with elevated concentrations of somatomedins might represent a pathogenetic subgroup.