Using a visual analogue scale, we compare the effect of patient-controlled analgesia and conventional intramuscular opioid regimen in 68 patients undergoing lower abdominal or gynecological surgery. We also recorded the incidence of side effects. We checked visual analogue scale 4 hours interval for 30 cases managed by patient-controlled analgesia and 38 cases of conventional intramuscular opioid group managed by obstetrician. We maintained fentanyl $0.33{mu}g/kg/hr$ and set self administrable bolus dose $5.0{mu}g$(lockout interval: 15 min) in patient-controlled analgesia group. Conventional intramuscular bolus injection group were administered meperidine 50 mg for 4 hour interval. Mean visual analogue scale scores obtained by patient-controlled analgesia group and intramuscular bolus injection group were $2.49{pm}0.67$ and $4.53{pm}1.28$(p<0.05). Side effects such as; no significant incidence of respiratory depression, urinary retention, postural hypotension, nausea, vomiting and pruritus were developed by either group. These results suggest that patient-controlled analgesia was more effective method compared with conventional intraumuscular opioid injection regimen for post-operative pain management.