Morphologic changes of spinal canal and dural sac during spinal movement (flexion-extension) were analysed and reported with the base of cross sectional anatomy, as early as 1942. After that, this movement was emphasized and used in myelography in many countries under the name of functional myelography, for accurate diagnosis of spinal stenosis of spinal stenosis as herniated disc, but not used commonly in Korea. Authors analysed functional myelographic findings of 78 cases, 37 of normal and 41 of surgically confirmed herniated herniated disc, to intend to confirm the necessity of spinal movement dudring myelography. the result were as follows; 1. In normal group, anterior border of dural sac is straight with flexion, but indented in extension at the level of intervertebral space and this indentation is less prominent at L5-S1. 2. In normal group with extension, posterior indentation of dural sac is more prominent at the level of intervertebral space than body, A-P diameter of dural sac is narrowed all the level of intervertebral space except L5-S1. and dural sac moved anteriorly (near to the posterior portion of spinal body or intervertebral space)at the level of L5-S1 and all spinal body. 3. In disc patient, anterior indentation of dural sac is persist in both views (flexion & extension) and much more exaggerated with extension, but less prominent at L5-S1. 4. In herniated dics with extension, anterior movement of anterior dural border at the level of L5-S1 is much ecreased than normal.