Sufentanil or a sufentanil-clonidine combination was evaluated to determine whether the basal rate in patient-controlled epidural analgesia (PCEA) might affect the daily consumption, quality of analgesia or incidence of side effects. Following Caesarean section delivery, 60 patients were randomly assigned to receive one of the four following PCA regimens (15 patients per group) for the relief of post-operative pain by the epidural route: sufentanil 2μg mL−1 in 0.9% NaCl, demand dose 5μg i.e. 2.5mL, (group S+ with, group S without an infusion at 2.5mL hr−1) or sufentanil 2μg mL−1 + clonidine 3μg mL−1, demand dose 5μg sufentanil + 7.5μg clonidine i.e. 2.5mL (group SC+ with and SC without an infusion of 2.5ml hr−1). The other PCA settings (Bard I PCA pump) were a lock out interval of 10 min and a 1h limit of 20μg sufentanil and 30μg clonidine i.e. 10mL. The parameters measured were the analgesic drug consumption and number of dose demands during the first 24h, pain scores at 6h intervals, side effects and quality of sleep. The concurrent infusion increased the dose requirements regardless of the content of the syringe. Consumption of sufentanil was the highest in those patients receiving the plain solution with a basal infusion. Clonidine addition reduced the dose requirements but only significantly in those receiving the background infusion. Patients treated with the mixture tended to reach lower pain scores than those receiving sufentanil only without basal rate. Patients receiving the mixture with basal rate requested significantly fewer additional demands compared with the three other groups, but this did not influence the quality of sleep. Since side effects were more frequently registered in the patients in this group, it was concluded that the optimum regimen was the sufentanil-clonidine combination but with deletion of the basal rate.