Objective: A randomized trial assessed the effectiveness of a 2-level strategy for implementing evidence-based mental health treatments for delinquent youth. Method: A 2 x 2 design encompassing 14 rural Appalachian counties included 2 factors: (a) the random assignment of delinquent youth within each county to a multisystemic therapy (MST) program or usual services and (b) the random assignment of counties to the ARC (for availability, responsiveness, and continuity) organizational intervention for implementing effective community-based mental health services. The design created 4 treatment conditions (MST plus ARC, MST only, ARC only, control). Outcome measures for 615 youth who were 69% male, 91% Caucasian, and aged 9-17 years included the Child Behavior Checklist and out-of-home placements. Results: A multilevel, mixed-effects, regression analysis of 6-month treatment outcomes found that youth total problem behavior in the MST plus ARC condition was at a nonclinical level and significantly lower than in other conditions. Total problem behavior was equivalent and at nonclinical levels in all conditions by the 18-month follow-up, but youth in the MST plus ARC condition entered out-of-home placements at a significantly lower rate (16%) than youth in the control condition (34%). Conclusions: Two-level strategies that combine an organizational intervention such as ARC and an evidence-based treatment such as MST are promising approaches to implementing effective community-based mental health services. More research is needed to understand how such strategies can be used effectively in a variety of organizational contexts and with other types of evidence-based treatments. (Contains 2 figures and 5 tables.)