Purpose: To compare differences in BMI, body weight perception and satisfaction, and eating behavior by gender among middle school students. Methods: From 19 middle schools in W city four classes in two middle schools were selected by cluster sampling with multi-stage sampling. A structured questionnaire was answered by 143 adolescents. Results: Differences in BMI between boys and girls were significant (x$^2$=13.15, p=.00l). Boys reported higher ideal body weight than girls (t=6.33, p<.000l), and discrepancy between ideal body weight and body weight perception in girls was significantly greater than in boys(t=-5.0l, p<.0001). There was no significant gender difference in body weight perception but more boys were satisfied with their body weight(t=-4.48, p<.0001). Comparison of eating behavior showed that girls reported high scores in disinhibition (t=-2.29, p<.05) and hunger (t=-2.81, p<.01), while boys reported higher scores in cognitive restraints (t=3.22, p<.01). Conclusion: Interventions to help girls improve body image and satisfaction with body image are crucial. In order to establish proper diet habits and balanced nutritional status for adolescents, educational interventions should address characteristics of eating behaviors.