Deterrence is an established theme in criminal justice, but its role in prevention of assault has been treated with ambivalence and even hostility in medicine. The extent to which offenders can be persuaded, through knowledge of criminal and health risks, not to injure others is emerging from studies of the health effects of firearm and other crime legislation, and from macro-level studies and controlled experiments of police interventions. There is convincing evidence that motorists can be deterred from alcohol-impaired driving, and recognition that specific, targeted, and visible police work and increasing certainty of punishment are effective interventions. By contrast, duration of imprisonment and generic police initiatives such as blanket increases in police numbers seem to have little effect on deterrence, at least in the context of the decline in US homicide rates since 1991, to which demographic and economic factors seem to have contributed little. Together with established and cost-effective preschool education and early family support, targeted policing and increasing rates of conviction should be integrated into strategies for injury prevention.