In children with infantile autism or atypical pervasive developmental disorders somatic aspects play an important role. A review is presented of important hereditary, pre-, peri- and neonatal factors, findings at neurological examination, specific medical disorders and neurochemical and neurophysiological findings. Results of the medical examination of 15 children with autistic or atypical developmental disorders are presented. It is concluded that extensive medical examination of these children is indicated: in 8 out of 15 children a clinically relevant chromosomal, neurological or biochemical disorder could be detected.