The contribution of genetic, constitutional and environmental factors to the clinical polymorphism of schizophrenia was analysed. A sample from 353 pedigrees of the patients suffering from the manifest forms of schizophrenia which inhabited five districts of Tomsk region was studied using multifactorial threshold and single locus diallele models. It is established that the severity of the psychosis is mainly determined by autosomal genetic factors, the proportion of the affective disorders being specified by gonosomal factors. The type of the course of schizophrenia is closely connected with the patients' somatotype. Common environmental influences and peculiarities of personality before onset are linked with no characteristics of the clinical polymorphism studied.