The prevention of suicide requires an understanding of protective as well as risk factors, and the recognition of high-risk groups. Factors which increase the risk in patient populations include previous parasuicide, recent relapse or discharge, features of mental state (depression, psychosis), social circumstances (isolation, unemployment), and demographic characteristics (male sex, young age). Protective factors are under-researched but are likely to lie in the nature of psychiatric care. Consequently, community care may affect suicide by altering the level of protection at critical periods in an episode of illness. The clinical prevention of suicide should therefore be a priority for community services, and the relationship between suicide and mental health care should be researched by a national process of monitoring.