Objective.To c ompare the analgesic efficacy and adverse effects of patient-controlled analges iawith tramadol and with morphine for postoperative middle or severe pain .Methods.Fifty-nine patients

scheduled for elective hysterectomy or hystero myomectomy

were ran-domly divided into Group Tand Group M.The2drugs were administered intravenously v ia a patient-controlled analgesia device till24h postoperatively.Efficacy wa s assessed by comparing total pain reliefand the sum of pain intensity differencevalues over24h.Results.Statistically significant equival ence of tramadol and morphine was shown by TOTPAR values（15.9±4.4and1 6.4±3.5

respectively）and SPID values（9.2±4.7and9.0±2.0

respectively）.Tramadol caused fewer adverse events than morphin e（16.7%and26.7%of patients

respectively）.Conclusion.The analgesic efficacy of PCA with tramadol and with morphine were equivalent in the treatme nt of postoperative pain

and tramadol can cause slighter gastrointestinal adve rse effects.