​Probation services throughout the world have difficulty in assessing the risks and needs presented by offenders, in evaluating the effectiveness of supervision, and in enabling practitioners to assess the impact of their work with individual offenders. This paper describes how these problems are addressed by the comprehensive and relatively successful approach to evidence-based probation that has been developed since 1996 in the small Probation and After-Care Service of the British Channel Island of Jersey. In conclusion, the authors discuss whether such approaches could work in other jurisdictions, and suggest that this depends partly on context. In particular, the example of England and Wales shows how potentially successful approaches can be frustrated by over-centralization, managerialism and the politicization of criminal justice.