Objective To compare the efficacy of patient-controlled epidural analgesia (PCEA) with different concentrations of sufentanil plus levobupivacaine after caesarean section.Methods Ninety ASA Ⅰ or Ⅱ nulliparous patients who were at full term with a singleton fetus,aged 22-35 yr,weighing 60-85 kg,undergoing elective caesarean section under combined spinal-epidural anesthesia,were randomly divided into 3 groups (n =30each):0.125％ levobupivacaine plus sufentanil 0.4,0.6 and 0.8μg/ml groups (groups Ⅰ,Ⅱ and Ⅲ).The patients received 48 h of PCEA after operation.PCEA pump was set up with a background infusion of 2 ml/h,and a bolus dose of 2 ml with a lockout-interval of 15 min after a loading dose of 5 ml.VAS score was used to assess the intensity of pain (0 =no pain,10 =worst pain).VAS score ≤ 3 was considered as effective analgesia.VAS score ≥4 was considered as failure of analgesia,and the rescue analgesic was given.Venous blood samples were taken before operation and at 24 and 48 h after operation to detect the serum prolactin (PRL) concentration using radioimmunoassay.The degree of motor block of lower extremities was assessed and scored using modified Bromage scale.Maternal colostrum time,the number of attempts,and adverse effects including nausea and vomiting,pruritus,somnolence,respiratory depression,bradycardia,hypotension and urinary retention were recorded after operation.Results Compared with group Ⅰ,the number of attempts and rate of failure of analgesia were significantly decreased,the maternal colostrum time was shortened,and the serum PRL concentration at 24 and 48 h after operation was significantly increased in groups Ⅱ and Ⅲ,and the incidences of adverse effects such as nausea,vomiting and bradycardia were increased in group Ⅲ (P ＜ 0.05).Compared with group Ⅱ,no significant change was found in the number of attempts,rate of failure of analgesia,maternal colostrum time,and serum PRL concentration at 24 and 48 h after operation (P ＞ 0.05),and the incidences of adverse effects such as nausea,vomiting and bradycardia were increased in group Ⅲ (P ＜ 0.05).There was no significant difference in the modified Bromage scores among the three groups (P ＞ 0.05).Conclusion When sufentanil plus 0.125 ％ levobupivacaine are used for PCEA,the recommonded concentration of sufentanil is 0.6 μg/ml.