Background: The analgesic efficacy and safety of propacetamol, an injectable prodrug of acetoaminophen, in combination with intravenous morphine PCA were studied in 40 patients after gynecological surgery requiring lower abdominal incision. Methods: Using a double-blind, randomized, parallel-group design, the effects of four(every 6 hr) intravenous injections of 2 g propacetamol(=1 g acetoaminophen) were compared with four injections of placebo(PL) immediately after surgery. Efficacy of cumulative dose of morphine and number of boluses requested was assessed over 24 hours by automated recording on the PCA device. It was assessed on pain scores rated on a ten-point verbal scale along with vital signs, $K^+$, glucose, BUN, creatinine, PT and PTT were measured along with stress hormones(epinephrine, norepinephrine and cortisol). Results: There were no differences in demographic data between two groups. Propacetamol group demonstrated approximately 21% morphine sparing effect compared to placebo group($33.1{pm}10.4$ mg vs $41.4{pm}8.0$ mg). No significant differences noted in $K^+$, glucose, BUN, Creatinine, PT and PTT levels. There were significant increases in norepinephrine and cortisol in placebo group postoperatively, compared to preoperative values. At the same time, propacetamol group also showed significant changes in these hormones. Both group revealed high degree of patient satisfaction. Conclusion: Propacetamol showed significant morphine sparing effect to some degree. Side effects were much less in propacetamol group with subsequently high patient satisfaction. The secretion of stress hormone were not blocked by postoperative propacetamol injections. Authors concluded that propacetamol should be considered as an excellent adjuvant analgesics in postoperative pain control in opioid patient controlled analgesia.