In a retrospective study of 80 chronic DSM III-R schizophrenics and 80 controls, the occurrence of obstetric complications (OCs) into the development of chronic schizophrenias was investigated using Leonhard's distinction in systematic schizophrenia (no obvious familial loading) and unsystematic schizophrenia (mainly genetically determined according to Leonhard). The Lewis & Murray and Fuchs scales were used for evaluation. In both scales, unsystematic schizophrenias did not differ from controls, but those with OCs were significantly (p < 0.01) earlier hospitalized (20.5 years) than those without OCs (25.6 years). Systematic schizophrenics had an increased frequency, severity and total score of OCs compared to controls in the Fuchs scale (p < 0.01). Likewise, in the Lewis & Murray scale systematic schizophrenia showed an increased presence of OCs compared to controls (p < 0.05) and to unsystematic schizophrenia (p < 0.1). Systematic schizophrenias were significantly allocated to maternal infectious diseases during mid-gestation. Patients with maternal infections showed more additional OCs than those without (p < 0.05; Lewis & Murray scale). In systematic schizophrenia, a history of OC was not associated with an early onset of the disease. In the genetic determined schizophrenias prenatal and perinatal disturbances lead to an early onset of the disease, however, in systematic schizophrenias they seem to be of causal importance for the development of the disease.