ABSTRACT: IMPORTANCE:Lack of robust program evaluation has hindered the effectiveness of school-based drug abuse prevention curricula overall. Independently evaluated randomized controlled trials (RCTs) of universal, middle school-based drug abuse prevention curricula are the most useful indicators of whether such programs are effective or ineffective. OBJECTIVE:To conduct a systematic review identifying independently evaluated RCTs of universal, middle school-based drug abuse prevention curricula; extract data on study quality and substance use outcomes; and assess evidence of program effectiveness. EVIDENCE REVIEW:PsycInfo, Educational Resources Information Center, Science Citation Index, Social Science Citation Index, Cumulative Index to Nursing and Allied Health Literature, MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews were searched between January 1, 1984, and March 15, 2015. Search terms included variations of drug, alcohol, tobacco, and marijuana use, as well as school, prevention, and effectiveness. Studies included in the review were RCTs carried out by independent evaluators of universal school-based drug prevention curricula available for dissemination in the United States that reported alcohol, tobacco, marijuana, or other drug use outcomes. Two researchers extracted data on study quality and outcomes independently using a data extraction form and met to resolve disagreements. FINDINGS:A total of 5071 publications were reviewed, with 13 articles meeting final inclusion criteria. Of the 13 articles, 6 RCTs of 4 distinct school-based curricula were identified for inclusion. Outcomes were reported for 42 single-drug measures in the independent RCTs, with just 3 presenting statistically significant (P?