Objective: A group dissonance-based eating disorder prevention program, in which young women critique the thin ideal, reduces eating disorder risk factors and symptoms, but it can be difficult to identify school clinicians with the time and expertise to deliver the intervention. Thus, we developed a prototype Internet version of this program and evaluated it in a preliminary trial. Method: Female college students with body dissatisfaction (N = 107; M age = 21.6 years, SD = 6.6) were randomized to the Internet intervention, group intervention, educational video condition, or educational brochure condition. Results: Internet and group participants showed greater pre-post reductions in eating disorder risk factors and symptoms than video controls (M ds = 0.47 and 0.54, respectively) and brochure controls (M ds = 0.75 and 0.72, respectively), with many effects reaching significance. Effects did not differ significantly for Internet versus group participants (M ds = -0.13) or for video versus brochure controls (M d = 0.25). Effect sizes for the Internet intervention were similar to those previously observed for group versions of this intervention. Conclusions: Results suggest that this prototype Internet intervention is as efficacious as the group intervention, implying that there would be merit in completing this intervention and evaluating it in a fully powered trial. (Contains 3 tables and 2 figures.)