Total body fat measurement by means of skinfold thickness was performed in 295 middle school girls in Suwon, Korea. Skinfold thicknesses on 4 sites, namely, arm, back, abdomen, and waist were obtained and fat was calculated using mean skinfold thickness (MSF) and the following formulas. % Fat=0.747 X MSF (mm)+l6.21 Fat (kg) =0.619 X MSF (mm) +3.31. The following results were obtained. 1. In 85 (age. 13 yr) of the first year class girls skinfold thickness was: arm 6.9mm; back 8.2; abdomen 8.3; waist 10.7mm, mean thickness was 8.5mm. Fat was 22.6 ± 1.56% body weight or 8.20¡¾2.68kg. Lean body weight was 31.93 ± 3.16kg. 2. In 107 (age : 14.2 yr) of the second year class girls skinfold thickness was : arm 7.6mm; back 9.7; abdomen 9.7; waist 12.4mm; and mean thickness was 9.8mm. Fat was 23.0±5.09% body weight or 9.36±1.87kg. Lean body weight was 34.29±1.76 kg. 3. In 103 (age : 15.1 yr) of the third year class girls skinfold thickness was : arm 7.6mm; back 10.3; abdomen 9.4; waist 11.9mm; and mean thickness was 9.8mm. Fat was 23.2±4.35% body weight or 9.36±1.18 kg. Lean body weight was 37.10±5.08 kg. 4. The ratio of mean skinfold thickness (mm) to body weight (kg) was 0.213 in 13 year old girls, 0.225 in 14 year, and 0.213 in 15 year old girls.