Background:The annual number of homicide convictions in England and Wales is increasing. Previous studies have highlighted the aetiological role of alcohol and drugs in homicide. Aims: To examine rates of alcohol and drug misuse and dependence in people convicted of homicide; the role of alcohol and drugs in the offence; the social and clinical characteristics of alcohol- and drug-related homicides; and the social and clinical characteristics of patients with dual diagnosis who commit homicide. Methods: A national clinical survey based on a 3-year (19969) consecutive sample of people convicted of homicide in England and Wales. Information on rates of alcohol and drug misuse/dependence, the role of alcohol and drugs in the offence and social and clinical characteristics of perpetrators were collected from psychiatric reports prepared for the court in homicide convictions. Detailed clinical information was gathered from questionnaires completed by mental health teams for those in contact with mental health services. Results: Of the 1594 homicide perpetrators, more than one-third (42%) occurred in people with a history of alcohol misuse or dependence and 40% in people with a history of drug misuse or dependence. Alcohol or drug misuse played a contributory role in two-fifths of homicides. Alcohol played a major role in 52 (6%) and a minor role in 364 (39%) homicides. Drugs played a major role in six (1%) and a minor role in 138 (14%) homicides. Forty-two homicides (17%) were committed by patients with severe mental illness and substance misuse. Alcohol- and drug-related homicides were generally associated with male perpetrators who had a history of violence, personality disorders, mental health service contact and with stranger victims. Conclusions: Substance misuse contributes to the majority of homicides in England and Wales. A public health approach to homicide would highlight alcohol and drugs before severe mental illness. (Author' s abstract)