In a meta-analysis on controlled outcomes evaluations of 22,000 sex offenders, Losel and Schmucker found 80 comparisons between treatment and control groups. The recidivism rate averaged 19% in treated groups, and 27% in controls. Most other reviews reported a lower rate of sexual recidivism in treated sexual offenders. Of 2039 citations in this study (including literature in five languages), 60 studies held independent comparisons. Problematic issues included the control groups; various hormonal, surgical, cognitive behavioral, and psychotherapeutic treatments; and sample sizes. In the 80 studies compared after the year 2000, 32% were reported after 2000, 45% originated in the United States, 45% were reported in journals, and 36% were unpublished. Treatment characteristics showed a significant lack of pharmacologic treatment (7.5%), whereas use cognitive and classical behavioral therapy was 64%. In 68% of the studies, no information was available on the integrity of the treatment implementation; 36% of the treatment settings were outpatient only, 31% were prison settings, and 12% were mixed settings (prison, hospital, and outpatient). Integrating research interpretations is complicated by the heterogeneity of sex offenders, with only 56% being adult men and 17.5% adolescents. Offense types reported included 74% child molestation, 48% incest, and 30% exhibitionism. Pedophilia was not singled out. Follow-up periods varied from 12 months to greater than 84 months. The definition of recidivism ran the gamut from arrest (24%), conviction (30%), charges (19%), and no indication (16%). Results were difficult to interpret because of the methodological problems with this type of study. Overall, a positive outcome was noted with sex offender treatment. Cognitive-behavioral and hormonal treatment were the most promising. Voluntary treatment led to a slightly better outcome than mandatory participation. When accounting for a low base rate of sexual recidivism, the reduction was 37%, which included psychological and medical modes of treatment. Which treatments will reduce recidivism rates in sex offenders is extremely difficult to conclude. Some treatment effects are determined from small studies; however, recidivism rates may be based on different criteria. Larger studies tend to be published more frequently than small studies, negative results may be less likely to be reported in published studies, and differences in mandatory versus voluntary treatment may occur. Clearly more high-quality outcome studies are needed to determine which treatments work best for which individuals. One size is unlikely to fit all. However, pharmacologic intervention, although not always the perfect choice, has improved and will continue to advance the treatment of paraphilic, nonparaphilic, and compulsive sexual behaviors.