We report a case of symptomatic epidural gas accumulation after open diskectomy, causing lumbar radiculopathy. Surgery had been performed in a 44-year-old man for disk extrusion; however, he was readmitted to the hospital with increased lower back pain 5 months after the operation. CT and MR studies demonstrated accumulation of gas in the lumbar epidural space compressing the dural sac and nerve root. Symptoms disappeared after surgical removal of the gas.