The purpose of this study was to examine the relative importance of everyday life stress, obesity stress, and social support on the BMIs of junior high school students. Subjects in this study consisted of 229 adolescents from two junior high schools in Iksan-city and Hamyul-eup. For data analyses, the frequencies, percentages, means, t-tests, Chi-squares, one-way ANOVAs, Pearson's correlation coefficients and regressions were conducted using SPSS WIN program. The mean BMI of the subjects was 20.18, and the ratio of students' BMIs less than 20 was 56.8%, that of students' BMIs greater than or equal to 25 was 8.3%. There were no statistical differences in BMIs by grade and sex. Statistically significant differences in the obesity of the junior high school students were detected according to demographic characteristics such as economic levels, areas of residence, TV watching time, and fathers' physiques. There were significant differences in everyday life stresses, obesity stresses, and social support by sex, but not by grade. Girls showed higher stress levels than boys, specially in family-related life stresses, social relationships, and self-related stresses. Also girls showed higher stress level related to obesity than boys. Girls got more support from their mothers, siblings and friends than boys. With respect to the type of social support, girls perceived more financial, informational, emotional, and judgemental support than boys. These results suggest that girls became more stressed, although on the other hand, they received more social support than boys. The higher the economic level, the longer the TV watching time, and the higher the stresses from everyday life and obesity, the higher the BMIs of the junior high school students were. In conclusion, everyday life stress and obesity stress were the important factors in relation to the junior high school students' obesity.