The use of epidural injection of local anesthetics with steroid for the treatment of back pain and sciatica is a widely used procedure. There have been several reports about spinal cord compression by granuloma or fibrous mass related to intrathecal or epidural morphine injection. There have been also some reports about arachnoiditis after epidural injection of steroid. However, there have been no reports regarding dural sac or nerve root compression by fibrous mass after epidural steroid injections. We would report a case of dural sac and nerve root compression secondary to the formation of fibrous mass in the lumbar epidural space after epidural steroid and local anesthetic injections. In this case, the characteristic radiologic findings before and after epidural injection therapy and clinical progress were documented.