【Abstract】Objective To investigate the effect of patient-controlled intravenous analgesia (PCIA) with tramadol on the serum levels of interleukin-2 and interleukin-6 during laparoscopic cholecystectomy. Methods Forty ASAⅠorⅡpatients aged 20-60yr undergoing laparoscopic cholecystectomy were randomly divided into 2 groups (n=20 each): fentanyl group(Ⅰ) and tramadol group(Ⅱ). Anesthesia was induced with fentanyl 0.002 mg/kg, midazolam 0.02mg/kg ,propofol1~2mg/kg and rocuronium 0.6~0.8mg/kg. Anesthesia was maintained with inhalation sevoflurane( 1.5% ~3.0%) . PCIA was commenced at the end of surgery and continued for 24h. In Ⅰgroup PCIA with fentanyl1.0 mg+ Tropisetron Hydrochloride 5 mg in 100 ml of normal saline. The PCIA settting was: loading dose fentanyl 0.05mg; background infusion 2ml/h; bolus 2ml; lock-out interval 15 min and 1h limit 10ml. In Ⅱgroup PCIA with tramadol 600mg+ Tropisetron Hydrochloride 5 mg in 100 ml of normal saline. The PCIA settting was: loading dose tramadol 100mg ; background infusion 2ml/h; bolus 2ml; lock-out interval 15 min and 1h limit 10ml. The analgesic effect was assessed by VAS score, Ramsay sedation score, the number of effective button-pressing and side-effects such as nausea ,vomiting. Blood samples were taken immediately before induction and at 2, 4, 24h after surgery for determination of serum levels of IL-2 and IL-6 using enzyme-linked immunsorbent assay (ELISA). Results There were no significant difference in sex, age, body weight and duration of operation among the two groups（P>0.05）. The postoperative analgesia was satisfactory in both groups, and there was no significant difference in VAS score, ramsay score and the number of effective button-pressing between the two groups（P>0.05）. No vomiting and respiratory depression were observed in both groups. The serum levels of IL-2 increased significantly at 2, 4, 24h after surgery compare with the before anesthesia inⅠandⅡgroup（P<0.05）. The two groups was no significant difference between the two groups（P>0.05）. The serum levels of IL-6 no significantly difference at 2, 4, 24h after surgery compare with the before anesthesia inⅠandⅡgroup（P>0.05）. There were no significant difference in the serum of levels IL-6 in both group（P>0.05）. Conclusion PCIA with tramadol after laparoscopic cholecystectomy not only to provides adequate analgesia and can promote the immune function，inhibite the stress response.