The purpose of this study was to determine the extent to which refusal skills and norm setting mediated the impact of a school-based prevention program from the Alcohol Misuse Prevention Study (AMPS) on adolescent alcohol overindulgence. The AMPS is a randomized, pre-post, experimental-control study. Respondents in the present study included 6th through 10th graders (ns ranged from 232 to 371). Structural equation modeling analyses using EQS indicated that norm setting mediated the effect of the intervention on alcohol overindulgence at the 7th through the 8th grade and at the 8th through the 10th grade. In contrast, although the prevention program served to increase refusal skills, refusal skills did not mediate the effect of the program on alcohol misuse.