Combined spinal epidural block with use of the needle-through-needle technique has become increasingly more popular during recent years because it provides rapidity and density of spinal block, combined with the ability to extend the block and provide postoperative analgesia by use of the extradural catheter. However, the combined spinal epidural block has some disadvantages. Since the spinal needle makes a hole in the dura, the accidental migration of an extradural catheter into the dural opening made previously by the spinal needle is thought to be theoretical risk. We report a case during combined spinal epidural anesthesia for a total hip replacement in which the clear fluid in the epidural catheter was found and tested to confirm the nature of fluid and migration of catheter by the dextrostix test and the immunoelectrophoresis test(prealbumin test).