Project DARE (Drug Abuse Resistance Education) is the most prevalent school-based drug-use prevention program in the United States, but there is little evidence of its effectiveness. Results from a longitudinal evaluation of the program in 36 schools in Illinois provide only limited support for DARE's impact on student's drug use immediately following the intervention, and no support for either continued or emerging impact on drug use 1 or 2 years after receiving DARE instruction. In addition, DARE had only limited positive effects on psychological variables (i.e., self-esteem) and no effect on social variables (e.g., peer resistance skills). Possible substantive and methodological explanations for the relative lack of DARE's effectiveness observed in this study are discussed.