Epidural injection of morphine is widely used for relief of postoperative pain. However urinary retention, the side effect, following epidural morphine is troublesome for patient. A 45 year old male patient was admitted due to avascular necrosis of right hip joint and received bipolar endoprosthesis under continuous epidural anesthesia with 2% lidocaine 15 ml. In recovery room after operation, we applied 2 day,s continuous drug infusor (Baxter Infusor(R), Baxter Healthcare Co., USA) with morphine 2 mg and fentanyl 300 g in saline through epidural catheter. At 2 hour after operation, morphine 2 mg was added to the continuous drug infusor due to severe surgical pain. In ward, at 5 hour, he complained of voiding difficulty and abdominal distension. At 6 hour, Nelaton catheter was inserted and 1000 ml of urine was voided. On the 1st postoperative day, the continuous drug infusor was removed and he received naloxone 0.1 mg, two times, intravenously. But voiding difficulty was persisted. Intermittent Nelaton catheter or indwelling Foley catheter was inserted alternatively. Bethanechol chloride (Besacholine(R)) 15~90 mg/day and prazosin hydrochloride (Minipress(R)) 2~3 mg/day were administered orally and hot bag was applied on lower abdomen. On the 25th postoperative day, he was ultimately released from voiding difficulty and discharged without any problems. We suggested that the causes of urinary retention were bladder atony by overdistention of the bladder and contraction of internal urethral sphincter following epidural anesthesia, surgical pain and immobilization.