The kinetic of the distal radioulnar joint(DRUJ) is complex. Motion of DRUJ consists of rotation of the around the relatively stationary ulna, poisoning of the ulna along its longitudinal axis, and translational motion, which occurs in the antero-posterior plane. In addition to the motions described, there also exists and abduction-adduction movements, diastatic motion. The CT scan is an ideal tool for evaluation the DRUJ. Since it provides a coronal cross-sectional image of the radius and ulna. The amount of translational motion occurring at the DRUJ has hot been determined. To evaluate the normal boundaries of the motion of the DRUJ, forty DRUJ in twenty normal volunteers(10 meles, 10 females) were evaluated by use of a computed tomography technique. The results were as follows. 1. Average translational motion according to forearm rotation was 3.1mm±1.3. 2. There was no statistic difference between both sex(p>0.05). 3. There was no statistic difference between dominant and nondominant hand(p>0.05). The contralateral criterion is useful in determing wrist problem.