The prevalence of obesity and its related factors in adolescent girls in Seoul area were investigated from April, 18 to June, 29 1985 bymeans of anthropometry, dietary intakes and general environmental factors. Nine hundred and sixty junior high school girls were selected and invterviewed for 24-hour food intakes. Weight, height, a 우 skinfold thickness(triceps, abdominal) were measured and information on the general backgroun of the subjects were obtained by questinnaire. Subjects were divided into six groups according to their relative weights. It was observed that majority of the parents were under fifty years old and had high school education . In general, father was older and higher in educational levels than mother. Two thirds of subjects lived in their own houses and had three to four siblings. AVerage weight and height of subjects were 46.0kg and 154.4cm, which were higher than Korean natianl average. Average relative weight was 29.75 and average Kaup index was 1.925. Skinfold thickness was 13.4mm fo rtricepts and 16.4mm for abdominal . Prevalence of obesity was 12.9% and 4.8% by criteria of relative weight and skinfold thickness. Average intakes of most of nutrients except iron were acceptable but about one third of the subjects had less than 2/3 of RDa for calcium, iron, vitamin A, and riboflavin. As a whole, prevalence of obesity in this study was higher than those observed in the past surveys. Relationship of dietary intakes and general environmental factors that seemed to influence the obesity were integrated as such. As parents educational levels were higher, it tended to be higher in living standard and have fewer family members and siblings. These may influence more nutrient intakes so that fatness of the subjects seemed to be greater. In the meantime, parents fatness was closely related to those of children indicating an involvement of genetic factors. And also, food habits of individuals such as frequency of snack and bedtime snack were related to fatness significantly.