CT and myelography are the most accurate diagnostic tools to define a lumbar herniated disc disease. But theymay not demonstrate organic lesion of the cause of clinical symptoms or may not agree the site of lesion andlateralizing sign, so they may give a confusion to radiologist and clinicians. The purpose of this study is toestimate the value of lateral bending as functional myelography in the evaluation of the change of filling ofnerve root sleeve compared with that of static myelography. We analysed 84 disc spaces of 28 patients of bulgingdisc or central HNP who had undergone both lumbar CT and functional myelography at Pusan national UniversityHospital from Aug. 1987 to Aug.1988. The results were as follows: 1. In normal disc, there were tendencies of thesame or incresased filling of nerve root sleeve in the flexion site of lateral bending in functional myelographycompared with that of static myelography, and of the same or decreased filling of nerve root sleeve in theextention site of lateral bending in functional myelography. 2. In bulging disc and central HNP, diagnossticmethod of functional myelography incresased agreement of clinical symptoms and imaging diagnosis regarding thechange of filling in nerve root sleeve in functional myelography from static one as functional impairment of nerveroot. 3. Lateral bending in functional myelography was expected as precise and genuin diagnostic tool that mightrepresent functional impairment of nerve root.