The purpose of this study was to define Korean adolescent girls' brassiere size demand features in order to improve the suitability of junior brassieres for adolescent girls. The subjects for the data collection were Korean teenage girls from age 13 to 17 (n=492). Their body size was collected by conducting anthropometric measurement. The results of this study show that not only the growth of height, but also the growth of the body length is almost finished at the age of 15. The brassiere cup size, which shows the breast growth directly, increased remarkably at age 13 to 14, and once again at age 17. The demand for brassiere band size 70 appeared generally high among all ages. The research also suggests that the band size 60 and over 85 is also needed among the teenage girls. In matters of the brassiere cup size, junior brassieres over B-cup size are also necessary for teenage girls with big breasts to support their heavy breast weight. These results imply that the junior brassiere companies should improve their brassiere size range to fit the teenage girls' breasts properly.