Clinically unsuspected, usually neurodevelopmental, brain lesions of aetiological relevance occur in 6-10% of schizophrenic patients. About 3% of secondary schizophrenia arises in the presence of systemic physical illness, Psychopathology is not helpful in distinguishing secondary from primary schizophrenia. However, it is important to detect this organic-based subtype, since recognition and treatment of the primary disorder is needed. Therefore a set of standard investigations is needed to screen such cases when admitted with acute psychosis. The existence of secondary schizophrenias offers several potential pathways towards determining the cause of primary schizophrenia.