CT and myelography are the most accurate diagnostic tools to define a lumbar herniated disc disease. But they may not demonstrate organic lesion of the cause of clinical symptoms or may not agree the site of lesion and lateralizing sign so they may give a confusion to radiologist and clinicans. The purpose of this study is to estimate the value of lateral bending as functional myelogra-phy in the evaluation of the change of filling of nerve root sleeve compared with that of static myelography. We analysed 84 disc spaces of 28 patients of bulging disc or central HNP who had undergone both lumbar CT and functional myelography at Pusan national university Hospital from Aug. 1987 to Aug. 1988. The results were as follows: 1. IN normal disc there were tendencies of the same or increased filling of nerve root sleeve in the flexion site of lateral bending in functional myelography compared with that of static myelography and of the same or decreased filling of nerve root sleeve in the extention site of lateral bending in functional myelography. 2, IN bulging disc and central HNP diagnostic method of functional myelography increased agreement of clinical symptoms and imaging dignosis regarding the change of filling in nerve root sleeve in functional myelography from static one as a functional impairment of nerve root 3. Lateral bending in functional myelography was expected as precise and genuine diagnostic tool that might represent functional impairment of nerve root.