The diagnostic accuracy of myelography, electromyography, and clinical-neurological findings in 64 patients on whom the presence of herniated intervertebral disc was proved surgically from March, 1974 to February, 1980 in Severance Hospital was discussed and the results of this study was compared with those in comparable studies in the literature. 1. Of the cases in which operation revealed disc herniation or protrusion, the clinical neurological diagnosis was correct in 71.9%, the myelographic diagnosis was coincided in 79.7%, the electromyographic diagnosis was agreed in 73.4%. 2. In the patients which the patellar tendon reflex was weak or absent, operation revealed a herniation between L3 and L4 in 66.7%. The disc herniation bewteen L4 and L5 was noted in 93.0% of patients with weakness of the extensors of the great toe. Of the patients in whom the Achilles tendon reflex was weak or absent, operation revealed a tumbosacral disc herniation in 87.0%. 3. If the myelogram showed lumbar disc changes, these changes were confirmed at operation in the same level in all patients. 4. A disc herniation between L3 and L4 was demonstrated in aH cases of the patients had L4 denervation of the electromyographic findings. The disc herniation between L4 and L5 was seen in 93.0% of them had L5 denervation. A lumbosacral disc herniation was noted in 83.3% of them had 51 denervation. 5. Polyphasic motor units were significant in the absence of diagnosis of the herniated lumbar disc. 6. Signs of denervation in the spinal muscalature but not in the leg muscles were considered significant in patients with diagnostic problems of the lumbar radiculopathy. In summary, it is suggested that electromyography is not superior to the myeolgraphy or the clinicalneurogical examination. But the electromyography aids the surgeon in the dlagnosis of a compression lesion of a specific nerve root.