Substance abuse is a factor in some but not all incidents of crime: more than half of murders are committed when the killer is intoxicated. Males are more likely than females to be violent when consuming alcohol, and a past history of violence is predictive of future crime. The risk of violent behaviour is greater in subjects with dual diagnosis (e.g. alcohol dependence and psychiatric disorders). Offenders with an intellectual disability are overrepresented in prison and court populations, and more than 50% of them have a problem with alcohol. Since these subjects, in addition to intellectual disability and alcohol use, have psychiatric and behavioural problems, early recognition, in an effort to prevent future crimes, is an appropriate goal. Specific programmes have to address their particular needs.