There is a perception that people with a mental illness are dangerous. How ever, there are still arguments in the research literature as to whether the evidence supports this perception. The major aim if this paper is to review the findings if these studies in regard to the risk if violent behaviour in people with mental illness. An additional aim is to give an overview if the risk factors for violence in people with a mental illness. This systematic search if the literature resulted in good evidence that diagnoses such as schizophrenia and personality disorder are associated with an increased risk if violent behaviour. Substance abuse was the risk factor most associated with an increase in the risk if violent behaviour in' people with a mental illness. However, there are substantial differences in the methods used in studies if the risk in violence in people with mental illness resulting in a large variability in the estimates if risk. One if the major causes if variation may be due to the different difinitions if violence that are used. The need remains, therefore,for a meta-analysis of this literature based on clear definitions of violence in order to get a more accurate estimate if the risk of violence in people with a mental illness.