BACKGROUND: The preoperative administration of opioids recently has been evaluated for potential analgesic effects that extend beyond the duration of action of the opioids. The aim of this study was to compare the effect of balanced anesthesia using fentanyl-midazolam with inhalation anesthesia on the postoperative pain control and requirement of analgesics in the patients receiving intravenous patient- controlled analgesia (IV-PCA). METHODS: Sixty female patients scheduled for abdominal hysterectomy were divided into two groups. In group I (n=30), thiopental and succinylcholine were used at the induction of anesthesia and followed by N2O-O2-enflurane-pancuronium. In group II (n=30), thiopental, succinylcholine, fentanyl 2 microgram/kg and midazolam 0.1 mg/kg were used at the induction of anesthesia and followed by fentanyl- midazolam-N2O-O2-pancuronium. After surgery, patients were received IV PCA with 0.1% morphine. Visual analogue scales (VAS) for pain were recorded at 1, 2, 4, 6, 12, 24 and 48hr postoperatively and the consumptions of morphine, side effects and degree of satisfaction were noted. RESULTS: Hourly consumptions of morphine and rest and dynamic pain scores in group II were significantly less than in group I at first 1hr postoperatively. All the rest pain scores were less than 3 in both groups. CONCLUSIONS: The balanced anesthesia using fentanyl-midazolam reduced analgesic requirements and pain scores at first 1hr postoperatively compared with the inhalational anesthesia. However, we failed to show the potential preemptive analgesic effects beyond the duration of action of the opioids in balanced anesthesia.