Low back pain and sciatica is a common cause of physical disability and reduces the activity of the patient, which have a negative effect to a society and enigmatic to the concerned physician. Concerning to thecauses of low back pain and sciatica, direct mechanical compression exerted by protruded disc material on nerve roots has been widely accepted as a main factor. There is, however, a good deal of indirect evidence, which suggests that inflammatory changes, present in and around affected nerve roots, may also be of importance in the production of the pain. One hundred and twelve patients suffering from low back pain and/or sciatica.have been treated by epidural injection of methyl-prednisolone acetate 80mg and l% lidocaine 4cc, at Wonju Christian Hospital, Yonsei University Wonju Medical College from June, 1979 to April, 1983. Present study was done to analyse the effect of epidural steroid injection on low back pain and sciatica. The success of the injection was assessed strictly according to the subjective response of the patient. The results of this study are as follow: The overall effect of the epidural steroid injection; 26 patients(23%) were completely relieved of symptoms, 33 patients(29%) were markedly improved, 23 patients(21%,) were moderately improved, 30 patients(27%) stated that they had no relief from the injection. 2. As for a major causative disease of low back pain and sciatica, herniated lumbar disc, 65 patients(58%), was found. Secondly, 12 patients(11%) was degenerative spondylitis and 11 patients (10%) was lumbar sprain. 3. The patients who had only low back pain or sciatica without neurologic deficit showed much better improvement as 91 and 88. 4. A better result noted in the patients had symptoms for three months or less comparing with the patients having symptoms longer than three months. 5. The patients wiho had not been treated or concervatively treated prior to the injection represented better improvement comparing with the patients previously by surgical method. 6. Thirty eight(68%) of 56 patients who had history of trauma, and 44 patients(79%) of 56 patients who had no previous trauma history showed a moderate or better improvement. 7. No significant difference was found in the effect of injection according to ficdings of the routine roentgenography and myelography. 8. The patients who were responsible for the expenses of the treatment showed better improvement. 9. The symptoms were recurred in 19 patients(17%) within two months, and five of whom experienced marked and moderate pain improvement with second injection. The results suggest that the epidural steroid injection is relatively simple method with rere complication and more effective for treatment of low back pain and sciatica which may prevent the chronic pain when it is performed in the early stage with other conservative treatment.