In order to study how trunk flexion and trunk extension effect general motor ability and fundamental skills in soccer, 162 high school students ware examined from March till October, 1981. The conclusions emerged are as fellows: 1. Trunk fleaion, trunk extension and general motor abilities in soccer. Trunk flextion proved to be significantly correlates with all the items, except for "30m running", while trunk extension did not turn out to have any significant correlation with them, except "closedeye and one leg standing" and "back strength". 2. Trunk Flexion, trunk extension and fundamental skills in soccer. Trunk flextion showed itself to have significant correlation with all the Items, except for "dribble time", trunk extension displayed itself to be significantly correlates with "exactitude in shoot", "exactitude in instep kick", "throwing". 3. Analysis of predicting variations among trunk flextion, trunk extenion, and general motor abilities in soccer. ① Out of 28 percent of trunk flextion Predicting variation, "closed eye and one-leg standing" was 16 percent whick turned out to be the highest of all the items ② Out of 17 percent of trunk extension-predicting variations, back strength was 10 percent. which appeared to be the highest of the items. 4. Analysis of predicting variations among trunk flexion, trunk extension, and fundamental skills ill soccer. ① Out of 25 percent of trunk-extention-predicting variations, "heading" was 15 percent, which presented itself to be highest of all the items. ② Out of 13 percent of trunk extention-predicting variation, throwing was 10 percent, which indentified itself to have cross correlation with bath trunk flexion and trunk-extension.