The aim of this study was to evaluate the effectiveness of a school-based eating disorder prevention program designed to reduce dietary restraint and concern about shape and weight among adolescent girls. A total of 474 girls aged 13-14 years received the program as part of their normal school curriculum. An assessment-only control group included 386 pupils. Measures of eating disorder features, self-esteem, and knowledge were administered before and after the intervention and at 6-month follow-up. Immediately following the intervention, there was a small reduction in dietary restraint and attitudes to shape and weight in the index group, whereas there was no change in the control group. This reduction was not maintained at 6-month follow-up although the dietary restraint scores of the index group remained lower than those of the control group. This prevention program achieved change in eating attitudes and behavior, although the change was modest in size and not sustained. Focusing on a high-risk subgroup of dieters might be a more fruitful primary prevention strategy.