The science of effective offender rehabilitation remains a very young field: dominated theoretically and empirically by the work of a small group of Canadian psychologists. Their achievements include the ‘what works’ research literature, and the RNR model of offender rehabilitation. First disseminated in 1990, over the following 20 years, the Risk, Need and Responsivity Principles became the core of the theoretical framework used in those correctional systems around the world that use science as a basis for offender rehabilitation. This paper evaluates the strengths and weaknesses of the RNR model as a Level I rehabilitation framework. It proposes that unrealistic expectations and mistranslations of the model into practice are contributing to concerns about its validity and utility, and stifling needed innovation in the development both of mid-level treatment resources, and of RNR-adherent interventions. It concludes that although the RNR model's empirical validity and practical utility justify its place as the dominant model, it is not the ‘last word’ on offender rehabilitation; there is much work still to be done.