Accumulating evidence supports the hypothesis of abnormal neurodevelopment in schizophrenia. According to this hypothesis, schizophrenia is the consequence of prenatal abnormalities resulting from the interaction of genetic and environmental factors. In line with this hypothesis, several studies indicate that pregnancy and birth complications are risk factors for developing schizophrenia. At the clinical level, multiple cognitive deficits can be found in schizophrenic patients before illness onset. The neurodevelopmental hypothesis considers these cognitive deficits as the expression of early abnormalities on the central nervous system development. Consistently, brain imaging data show early structural abnormalities and abnormal progressive brain changes in schizophrenia. Finally, genetic and histological data indicate that genes associated with schizophrenia are involved in brain development.