The bone mineral densities of 60 middle school boys were measured with dual photon absorptiometry to define the influence of Taekwon-Do. They were divided into Taekwon-Do and control group, each comprising 30 boys. The bone mineral densities of the head, trunk, pelvis, both upper and lower extremities, and body total were measured. The results were as follows. 1. The BMD of head was 1.668 ± 0.153 in Taekwon-Do and 1.554 ± 0.153 0.167 in control. It was significantly increased in aekwon-Do(p <0.05). 2. The BMD of trunk was 0.378 ± 0.153 0.044 in Taekwon-Do and 0.353 ± 0.153 0.053 in control. There was no significant difference(p >0.05). 3. The BMD of pelvis was 1.648 ± 0.153 0.112 in Taekwon-Do and 1.444 ± 0.153 0.215 in control. It was significantly increased in Taekwon-Do(p <0.005). 4. The BMD of right and left legs were 1.597 ± 0.153 0.118 and 1.579 ± 0.153 0.125 in Taekwon-Do and 1.425 ± 0.153 0.115 and 1.421 ± 0.153 0.113 in control group respectively. They were significantly increased in Taekwon-Do(p <0.005). 5. The BMD of right and left arms were 1.184 ± 0.153 0.090 and 1.178 ± 0.153 0.115 in Taekwon-Do and 1.056 ± 0.153 0.095 and 1.066 ± 0.153 0.097 in control group respectively. They were significantly increased in Taekwon-Do(p.<0.005). 6. The total body BMD was 0.932 ± 0.153 0.068 in Taekwon-Do and 0.846 ± 0.065 in control. It is significantly increased in Taekwon-Do(p<0.005). In conclusion, Taekwon-Do increases the total bone mineral density and the mineral densities of the head, pelvis and extremities but not that of trunk. It is thought that continued practice of Taekwon-Do throughout adult life might prevent the senile osteoporosis