New information continuously alters scientific classifications and their applications. A revision in progress of the DSMâIVâTR, which concerns classification of disorders, predominantly of behavioral symptoms, suggests reconsideration of overlaps and differences between two broad families of developmental disorders: autisms and schizophrenias. Developmental disorders are classified within two independent domains: behavioral/descriptive (level A) and biologic/etiologic (level C). Level A classification is syndromic and based on aggregates of mostly continuous, dimensional features with indistinct margins. Etiologic level C classification is based largely on categorical interacting genetic and environmental factors responsible for level A syndromes. Level B encompasses biologic mechanisms (pathogenesis) linking etiology (level C) to behavior (level A). Many level B hierarchical molecular and cellular networks contribute to the structure and function of the many brain networks responsible for level A behaviors. Autism and schizophrenia share some behavioral and cognitive characteristics, pathogenic mechanisms and etiologies, but major clinical disparities (level A) separate them.