The purpose of this study was to compare the body compostition and aerobic and anaerobic abilities between low and high performance groups of female students in 12-min run. Hight, weight, % body fat, vertical jump, and 12-min run performance were measured on 437 female students. Their mean (±SD) va1tie of 12-min run performance was 2208.5±165.7m. Out of 437 girls tested, 9 girls (group L) whose 12-min run performace were lower than 1959m, and 14 girls (group H) whose performance were higher than 2457m volunteered as the subjects. The leg volume, Vo_2 max, anaerobic threshold (AT), Vo_2 at submaximal treadmill running, maximal leg strength, and maximal anaerobic power were measured. Group L differed significantly (p<0.001) from group H in Vo_2 max (38.5±2.2 vs 47.l±3.1ml). Vo_2 max per LBM of group L was also lower (15.9%) than that of group H , but muscle and bone volume of leg was similar in both groups . Group L tended to show the larger values in weight (4.6%), % body fat (10.0%), and Vo_2 at 130m/min (running economy) (5.4%)as compared with group H. There were no differences in AT, HR max, and maximal leg strength between the two groups. AT values of both groups appeared at about 62% of Vo_2 max. Maximal anaerobic power per body weight of group L was lower (11.47%, p<0.01) than that of group H, which was caused by the slow velocity of group L at the maximal anaerobic power on the force-velocity relationship. On results of mu1tiple-regression analysis predicting the 12-min run performance from other variables in the combined group, the relative importance of the independent variables as determinants of 12-min run performance were in order of Vo_2 max (ml/kg/min), running economy, and maximal anaerobic power per body weight. This multiple-regression equation accounted for 93.6% of the variance of 12-min run performance.