Systems of criminal sanctions around the world comprise both custodial and non-custodial sanctions. But what impact do custodial versus non-custodial sanctions have on the re-offending of those convicted of offences? Does a custodial sentence produce more or less re-offending than a non-custodial sanction? What does the research tell us?Systematic reviews are one means of helping people to pick their way through the jungle of research findings. Systematic reviews combine a number of studies that are considered to satisfy a list of empirical criteria for measuring effects as reliably as possible. The results of these studies are then used to calculate and produce an overall picture of the effects associated with a certain phenomenon. In this way, systematic reviews systematically produce a more reliable overview based on the best knowledge available.Report prepared for Brå by Patrice Villettaz, Gwladys Gillérionand Martin Killias