Objective: To determine the effectiveness of brief strategic family therapy (BSFT; an evidence-based family therapy) compared to treatment as usual (TAU) as provided in community-based adolescent outpatient drug abuse programs. Method: A randomized effectiveness trial in the National Drug Abuse Treatment Clinical Trials Network compared BSFT to TAU with a multiethnic sample of adolescents (213 Hispanic, 148 White, and 110 Black) referred for drug abuse treatment at 8 community treatment agencies nationwide. Randomization encompassed both adolescents' families (n = 480) and the agency therapists (n = 49) who provided either TAU or BSFT services. The primary outcome was adolescent drug use, assessed monthly via adolescent self-report and urinalysis for up to 1 year post randomization. Secondary outcomes included treatment engagement (greater than or equal to 2 sessions), retention (greater than or equal to 8 sessions), and participants' reports of family functioning 4, 8, and 12 months following randomization. Results: No overall differences between conditions were observed in the trajectories of self-reports of adolescent drug use. However, the median number of days of self-reported drug use was significantly higher, [chi][superscript 2](1) = 5.40, p less than 0.02, in TAU (Mdn = 3.5, "interquartile range" ["IQR"] = 11) than BSFT ("Mdn" = 2, IQR = 9) at the final observation point. BSFT was significantly more effective than TAU in engaging, [chi][superscript 2](1) = 11.33, p less than 0.001, and retaining, [chi][superscript 2](1) = 5.66, p less than 0.02, family members in treatment and in improving parent reports of family functioning, [chi][superscript 2](2) = 9.10, p less than 0.011. Conclusions: We discuss challenges in treatment implementation in community settings and provide recommendations for further research. (Contains 2 footnotes, 5 tables, and 3 figures.)