Purpose: The purpose of this study was to examine the relationship between body image, weight-control self-efficacy, and body mass index of high-school girls. Methods: Body image, gender role identity, weight-control self-efficacy, and body weight control behavior were measured by structured questionnaires. Date were analyzed by descriptive statistics, the t-test, the one-way ANOVA, and Pearson correlation, using the SPSS program. Results: Body weight control behavior was positively correlated with weight-control self-efficacy and objective body mass index. Body weight control behavior showed significant differences according to the interest in weight control, current weight control effort, reasons for weight control, secret method for weight loss, eating breakfast or not, and the amount of time exposed to mass media. In regard to the body weight control behavior according to the gender role identity type, the androgynous showed significantly higher tendency than other types. Conclusion: These findings suggest that health providers need to educate high-school girls about appropriate body image and weight control behavior. Also, more studies are needed to identify factors influencing weight control behavior.