This is a critical review of the literature related to the neurodevelopmental hypothesis ofschizophrenia which posits that the illness is related to abnormal brain development. The reviewfocuses on data deriving from clinical studies, and it is organized according to the life phase fromwhich the data were collected: conception and birth, infancy and childhood up to the onset of theillness, after illness onset, and postmortem. The neurodevelopmental hypothesis is supported byseveral pieces of evidence, including increased frequency of obstetric complications in patientswith schizophrenia; the presence of minor physical anomalies; the presence of neurological,cognitive, and behavioral dysfunction long before illness onset; a course and outcome of theillness itself that is incompatible in most cases with a degenerative illness; the stability of brainstructural measures over time; and the absence of postmortem evidence of neurodegeneration. Ahistorical perspective on how this research accumulated and a section addressing important areasof future investigation are also provided. We conclude that schizophrenia is certainly not adegenerative brain disorder, and that it is likely that a brain insult in utero or at birth plays a rolein its expression. Current evidence cannot completely exclude the role of environmentalvariables after birth. In addition, it is possible that other psychiatric disorders may also have aneurodevelopmental component.