CT may be valuably used indetermination of proptosis. Normal value of eyeball protrusion was measured innormal Koreans using CT. Among 86 Koreans, 26 have normal both eyes, but 60 have one normal eye with one abnormaleye (chiefly, proptosis and and eyeball tumor) The results of 112 eyes are as follows; Absolute measurement of“a”, that is, the distance between cornea & IZL (interzygomatic line) is 16.0±3.4mm in male (for 63 eye),15.7±4.0 mm in female for 49 eyes. Ratio of “a” over “A” (A-P diameter of eyeball) is 57±12% is male (for 63eye), 57±14% in female (for 49 eye) Discrepancy of eyeball protrusion between both eyes is 0.67±1.5mm (for 26adults) Practically, normal range of eyeball prototrusion(“a”) is 12.6mm< male< 19.4mm, 11.7mm