Neuropsychological, structural and functional imaging studies have broken new ground in demonstrating the existence of physiological and anatomical abnormalities in the olfactory system in schizophrenia. Since the pioneering psychophysical studies of odour recognition memory in patients with schizophrenia by Australian researchers Campbell and Gregson, a number of investigators have reported that schizophrenia patients exhibit olfactory dysfunction. In a 10-year longitudinal study, the presence of deviant olfactory experiences was found to significantly predict the development of future psychosis. The causes of olfactory impairments are numerous, including chemical, infectious, traumatic, metabolic and hormonal disturbances. Recent years have brought rapid expansion of structural and functional imaging technologies, including high-resolution structural magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission tomography (SPECT) and event-related potential (ERP). To characterise more directly the functional status of the olfactory system, ERPs have been employed to assess the physiological brain response to odour stimuli.