The Insitute of Criminology at the University of Cambridge recently undertook,at the behest of the Home Office, a comprehensive study of the literature on criminal deterrence, concentrating on recent research. The result, published in this book, examines the popular claim that 'deterrence works'. That it works in general terms is beyond dispute, but the claim most favoured by law-makers is narrower: that tougher sentences have a direct impact on criminal behaviour, limiting the number and severity of offences committed. This study seeks to discover the truth of that claim. Deterrence as a penal aim, is a broad subject, hence the authors of this work decided to look at two elements of recent research. First they looked at studies which examine the marginal deterrent effects of changing the certainty of punishment, that is, of altering the likelihood of an offender's being apprehended and convicted for a crime. Secondly they looked at studies of the marginal deterrent effects of altering the severity of punishment through changes in sentencing policy. It is their evaluation and analysis of the latter which is the principal focus of the work, and which will make the book essential reading for all those interested in sentencing and penal policy.