BACKGROUND: Surgical trauma and anesthesia are associated with postoperative immune suppression. Alterations in immune response have been suggested in the same surgery, according to anesthetic techniques. Therefore, this study was conducted to investigate whether regional anesthesia or premedication with clonidine change postoperative circulating neutrophils, lymphocytes and monocytes, and interleukin 6 (IL-6) responses. METHODS: Thirty patients undergoing elective low abdominal surgery were randomly divided into 3 groups: the control group and spinal group received no premedication and the clonidine group received general anesthesia with clonidine premedication. Blood samples were obtained to measure subpopulations of white blood cells (WBC) and IL-6 at pre-induction, immediately after the operation, and 24 h after incision. RESULTS: Increase in total WBC and percentage of neutrophils, decrease in percentage of lymphocytes and monocytes, and increase in IL-6 levels were significant after surgery, compared to the baseline values within the three groups. However, no significant differences of subsets of WBC and IL-6 level were seen among the groups throughout the study periods. CONCLUSIONS: Anesthetic technique did not influence the levels of circulating WBC and IL-6.