Most follow-up investigations of the effectiveness of specialized treatment for adolescents who have offended sexually have not included a comparison group. Furthermore, the average length of most previous studies is approximately 5 years. This investigation is a 10-year extension of our prospective, 10-year follow-up study of specialized treatment (Worling & Curwen, 2000). Recidivism data (criminal charges) were collected from a national database for 148 adolescents who had offended sexually. Adolescents were between 12 and 19 years of age (M = 15.5; SD = 1.5) at assessment, and the follow-up interval spanned from 12 to 20 years (M = 16.23; SD = 2.02). Relative to the comparison group (n = 90), adolescents who participated in specialized treatment (n = 58) were significantly less likely to receive subsequent charges for sexual, nonsexual violent, and nonviolent crimes. These data add to the growing body of research supporting the effectiveness of specialized treatment for individuals who have offended sexually. Copyright © 2009 John Wiley & Sons, Ltd.