 Abdominal surgery causes severe postoperative pain. Multi-modal pain therapy is usually applied but there is no perfect choice. It depends on physicians skill and situation. The best regimen is patient-controlled analgesia, but it requires an expensive equipment. Transdermal fentanyl patch, usually used in chronic pain relief, can steadily release fentanyl into blood stream for 72 hours, but it has slow onset of 12 hours. 