Recently, continuous epidural catheter insertion is usually employed in operation and chronic pain control. Delayed migration of an extradural catheter into subdural space or subarachnoid space is a rare but life threatening complication of continuous epidural catheter insertion, especially with out patients. The symptoms may include lower extremity weakness, hypotension, drowsy and respiratory depression. We experienced two cases of lower extremity paralysis due to delayed migration into subdural or subarachnoid spaces at our pain clinic. The tecnical procedures for continuous epidural catheterization went smoothly without any complications. However, clinical signs of lower extremity paralysis and sensory loss developed gradually, about 2 hours and 30 minutes after the continuous epidural injection. Two cases were confirmed by subdurogram and myelogram.