Previous studies have shown that patient-controlled analgesia(PCA) provides effective pain control in the postoperative patient. To compare the effect of pain relief on postoperative sympathetic responses and myocardial oxygen consumption, 40 healthy female patients undergoing abdominal hysterectomy were chosen randomly. They underwent pain management with either intravenous patient-controlled analgesia(IV PCA) or intermittent intramuscular opioid(IM P.R.N) regimen. Pain intensity(VAS), heart rate, blood pressure, and rate pressure product(RPP) were measured at predetermined time intervals for postoperative 72 hours after measurement of preoperative baseline values. Comparisons were then made between the two groups and among individuals within each group. IV-PCA improved postoperative pain relief(P<0.05), but did not suppress efficiently the heart rate, blood pressure, and RPP indicating sympathetic responses and myocardial oxygen consumption when compared with M P.R.N regimen. These variables were increased immediately and/or 30 minutes following the operation in both groups when compared with preoperative baseline value (P<0.05). These results suggest that improved pain relief per se by IV PCA had no mjor influence on the suppression of sympathetic responses and myocardial oxygen consumption and these responses were exaggerated during first 30 minutes after abdominal hysterectomy.