The role of eccentric muscle activities in functional everyday activities and sport is important and equally significant to concentric conditions. Eccentric and concentric exercise and evaluation are, therefore, very important. The purposes of this study were to measure eccentric and concentric peak torque, percentage of peak torque, average power and percentage of average power of trunk flexors and extensors by using the Cybex NORM isokinetic dynamometer, and to standardize the value obtained. Thirty four young volunteers were tested, 17 females and 17 males who had no history of back pain or abnormality. Each subjects were tested on three repetitions foe isokinetic concentric and eccentric contraction at 5 velocities. The results were as follows; 1) Peak torque percent body weight of eccentric contraction were significantly greater than concentric contraction at each angular velocity and in trunk flexors and extensors(p$lt;0.01). 2) Peak torque percent body weight of concentric contraction were significantly decreased as the angular velocity increased both male and female(p$lt;0.01). 3) Peak torque percent body weight of eccentric contraction were not significantly changed as the angular velocity increased both male and female(p$gt;0.05). 4) Peak torque percent body weight of male were significantly greater than female at each angular velociry and in concentric and eccentric contraction of trunk flexors and extensors(p$lt;0.01).