This paper describes psychological approaches to the treatment of sexual offenders. The empirically generated principles of effective treatment are outlined followed by the identification of the evidence-based issues that need to be addressed. The established important role of the therapists’ behaviors during treatment is then described along with the effectiveness of recruitment strategies and of tactics aimed at ensuring all entrants complete the program. Meta-analytic reports describing treatment efficacy are considered followed by an outline of the appraisal of the effectiveness of two large scale independent treatment programs. Finally, a brief description of a cost-benefit report indicates that when treatment of sexual offenders effectively reduces re-offense rates, it also saves a considerable amount of taxpayers’ money.