The epidemiology and aetiology of schizophrenias are discussed, including factors such as heredity, biochemical factors, constitution, premorbid personality, endocrines, neuropathology, precipitating factors and environmental factors. The psychopathology of simple schizophrenia, ebephrenia, catonic schizophrenia and peranoid schizophrenia are described. Differential diagnosis, prognosis, and outcome are discussed.