The randomly selected participants completed a required treatment program for serious sex offenders at a secure State-operated juvenile correctional facility in Wales, Wisconsin. The youths had been convicted or a serious sexual assault or had been convicted of a non-sex offense with a serious sexual assault on their record. The treatment program included group psychotherapy, general and special education, sex education, behavioral management, and some individual and family therapy. The treatment lasted an average of 8 months. The participants had been released from juvenile custody for a minimum of 10 years prior to the study. The research gathered information on further convictions, sentences, and care dispositions, including the type of offenses. The majority of the participants reoffended, but were not involved in another sexual assault. Twelve percent reoffended sexually, 66 percent were convicted of non-sexual offenses, and 22 percent were not convicted of any offenses during the follow-up period. Results revealed that the risk of sexual reoffense continued throughout the 10-year follow-up and that the majority of first sexual offenses after release occurred in the first 5 years. Recommendations for further research, tables, and 19 references (Author abstract modified)