The object of this study was to determine the physiological range of talar tilt angle of the Korean and to establish the basis for diagnosis and treatment of the lateral instability of the ankle. The anteroposterior inversion stress view of both ankles was taken in the 108 healthy Korean who had no history of ankle injury or disease. The sagittal stress films were also performed on 96 ankles (48 cases) of these to further define the physiological limits of the sagittal mobility of the normal talus. We compared these two values of normai mobility of talus to deterrnine the significance and relationship of the rwo. The results obtained were as follows: 1) Talar tilt over 10 degrees was seen in only 6 ankles (1.9%) and most of the ankles (279 ankles, 88.4%) showed a tilt less than 5 degrees. 2) Normal talar tilt angle was increased in 30 degrees plantarflexed position than in 90 degrees neutral position of ankle. In 12 cases the value was different between the right and the left; but there was no significant difference between the sexes. 3) The anterior displacement index over 200 was seen in only 5 ankles (5.2%). 4) There was gross positive inter-relationship between physiological. range of talar tilt angle and talar sagittal mobility.