We studied the effects of behavior modification and aerobic exercise on body weight, degree of obesity, % body fat, triceps skinfold thickness, blood pressure and eating behavior among overweight middle school girls. 15 girls participated in the behavior modification program by joining 60-90 minute group session weekly. The aerobic exercise program was given to 13 girls 3 times per week with 60 minutes each time. The data were obtained before treatment, after 4 and 8 weeks after treatment. In analyzing the data, repeated measures ANOVA were adopted. The results were as follows ; 1. For the changes of body weight between 2 groups, body weight of behavior modification groups decreased significantly than these of aerobic exercise group at 4 and 8 weeks after treatment, 2. For the changes of degree of obesity between 2 groups, there were no significant differences over time, 3. The analysis of change of % body fat did not reveal significant differences between 2 groups over time, 4. The changes of triceps skinfold thickness were significant differences between 2 groups over time, 5. For the changes of systolic blood pressure between 2 groups, there were significant differences over time. At 4 weeks after treatment, systolic blood pressure of behavior modification group decreased significantly than these of aerobic exercise group. 6. The changes of diastolic blood pressure were significant differences between 2 groups over time.