This was a three-stage sex offender treatment evaluation project that examined what kinds of community-based treatment for sex offenders were effective. Phase one of the study involved a review of research into the efficacy of programs in Europe and North America, as well as a survey of programs operated by or in conjunction with probation services in England and Wales. The review found that cognitive behavioral approaches were the most promising; these involved teaching offenders to reassess their attitudes toward victims and offending; behavioral controls were also taught. Work with sex offenders in England and Wales has, with few exceptions, used cognitive behavioral therapy. In the second phase of the project, seven community-based treatment centers were selected for further in-depth study by a team of psychologists. The third phase involved an examination of reconviction rates 2, 5, and 10 years after treatment. The study found that when compared with a sample of sex offenders put on probation in 1990, those referred to the seven programs were less likely to be reconvicted for a sexual offense (5 percent compared with 9 percent). This difference still held true when differences in the samples were taken into account. Of the 11 offenders who were reconvicted, 6 committed further sexual offenses, and 5 were convicted of a nonsexual, nonviolent offense. None of the 24 offenders who were assessed as having been significantly treated had been reconvicted within 2 years. This included nine who were assessed as being highly deviant before treatment. 3 tables and 6 references