The Computed Tomography is the most exact method to find out some diesase, soft tissue or musculoskeletal system. It is searching examination distinguishing normal structure and abnormal states in the spine and spinal canal. This is almost an absolute diagnostic method for spinal stenosis, and it has a special forte becasue it can distinguish the soft tissue around the spine. Thus we can distinguish metastatic cancer, herniated intervertebral disc, hypertrophy of the yellow ligament, and spine tumor very easily. Thirty-two cases of herniated intervertebral disc in lumbar spine were treated for 18 months from Jan. 1981 to Jun. 1982. Of thirty two cases, 18 cases were underwent CT scanning and 9 cases were underwent CT scanning and myelography. We obtained following results: 1. In the 18 cases taking a CT scan we found 6 cases of bulging annulus, 7 cases of herniated disc, one case each of facet syndrome, lateral recess syndrome, and three cases had normal finding. 2. In 9 cases taking CT scan, myelography and operation, 7 cases showed the same positive findings, but one case showed the positive CT scan and myelography, negative surgical exploration, and another case showed positive myelography, negative CT scan surgical exploration. 3. In 9 cases who took only a CT scan, there were 6 cases in which myelography was impossible or refused. Among these 6 cases 4 patients took operation and showed positive findings. 4. The diagnosis of herniated intervertebral disc by means of the CT scan has been made more accurately by the supplementary use of metrizamide and improvement of interpretation. a. When the patient refuses myelography. b. For discrimination of other diseases than herniated intervertebral disc. c. When the patient is allergic to iodine dyes used in myelography. As mention above, not only herniated intervertebral disc, but also many other diseases in spine can be diagnosed and we can decide that the herniated intervertebral disc surgery would by desirable with only the CT scan as nonivasive diagnostic test.