Many people with severe schizophrenia have increased cerebral ventricular size and diffuse reduction in cortical volume; recent attention has focused on subtle malformations of the cytoarchitecture in the hippocampus and parahippocampal cortex. Sufferers also show an excess of dermatoglyphic and minor physical abnormalities, and a significant proportion had psychomotor deficits, cognitive or behavioural problems as children. Such findings suggest that the form of schizophrenia most akin to Kraepelin's original description of dementia praecox results from neurodevelopmental impairment. This may have its origin in genetic defects in the control of early brain growth, or in early environmental hazards such as prenatal exposure to maternal influenza or perinatal complications. How foetal or neonatal lesions produce hallucinations and delusions two or three decades later remains a mystery, but maturational changes in the brain may be important.