A left handed, monozygotic, male twin developed schizophrenia, whilst his right handed brother was free of psychopathology. There was no family history of mental illness or left handedness. The affected twin had left side motor weakness and an EEG showed scattered irregularities, particularly on the left. Psychometry indicated left sided tempero-parietal dysfunction. The relationship between left temporal lobe damage and schizophrenia is considered.