In recent years neuroimaging techniques have revealed various cerebral and structural variances in patients with schizophrenic psychoses. The best established findings are the enlargement of the lateral ventricles and discrete structural deficits in temporobasal structures of the cortex. Neuropathological investigations have detected subcortical as well as cortical variances. Subcortically, the volume of the striatum and the globus pallidus have been found to be enlarged in schizophrenics. Among the cortical deviations, the cytoarchitectonic disturbances of the rostral entorhinal region have been well documented and are especially important. According to neuropathological criteria, they are derived from disturbances of prenatal cell migration within the central nervous system. Well documented are the architectonic changes in the rostral cingulate gyrus which is itself connected with the entorhinal region via the Papez circuit. These findings are supported and supplemented by the results of epidemiological studies which indicate a disturbance of brain development during the second trimester of the prenatal period. Viral infections (Influenza A2) of mothers during this critical period appear to play an especially important role. Nevertheless, the interaction between a genetic predisposition and exogenous noxious agents in such cases still needs to be clarified in our understanding of the etiology of schizophrenic psychoses.