A randomized clinical trial evaluated the efficacy of multisystemic therapy (MST) versus usual community services (UCS) for 48 juvenile sexual offenders at high risk of committing additional serious crimes. Results from multiagent assessment batteries conducted before and after treatment showed that MST was more effective than UCS in improving key family, peer, and academic correlates of juvenile sexual offending and in ameliorating adjustment problems in individual family members. Moreover, results from an 8.9-year follow-up of rearrest and incarceration data (obtained when participants were on average 22.9 years of age) showed that MST participants had lower recidivism rates than did UCS participants for sexual (8% vs. 46%, respectively) and nonsexual (29% vs. 58%, respectively) crimes. In addition, MST participants had 70% fewer arrests for all crimes and spent 80% fewer days confined in detention facilities than did their counterparts who received UCS. The clinical and policy implications of these findings are discussed.