Abstract
This article reviews the evidence on the deterrent effect of police and imprisonment. Studies of changes in police presences, whether achieved by changes in police numbers or in their strategic deployment, consistently find evidence of deterrent effects. Studies of the deterrent effect of increases in already long prison sentences find at most a modest deterrent effect. Three high-priority areas for future research are identified: developing and testing an integrated model of the effects of the threat and experience of punishment, measuring perceptions of sanction regimes, developing and estimating the deterrent effect of shorter prison sentences and identifying high-deterrence policies.