The authors investigated the effectiveness of 2 interventions in reducing eating disorder risk factors under naturalistic conditions in sororities. On the basis of previous research, the campus sororities chose to implement a semimandatory, 2-session eating disorder prevention program to all new sorority members (N = 90) during sorority orientation. To facilitate evaluation, sororities agreed to random assignment of new members to either a cognitive dissonance or a media advocacy intervention. Undergraduate peer facilitators ran the groups. Although both interventions had an effect, cognitive dissonance generally was superior at 8-month follow-up. Results further support the utility of cognitive dissonance in reducing eating disorder risk factors and suggest that nondoctoral-level leaders can deliver the program. Results also indicate that a semimandatory format does not reduce effectiveness.