Objective To compare the effects of different general anesthesia protocols on perioperative cellular immune function in patients undergoing laparoscopic surgery for colorectal cancer.Methods Ninety ASA Ⅰ or Ⅱ colorectal cancer patients,aged 40-64 yr,weighing 50-85 kg,undergoing laparoscopic surgery were randomly divided into 3 groups (n =30 each):group total intravenous anesthesia (group Ⅰ) ; group inhalational anesthesia(group Ⅱ) and group combined intravenous-inhalational anesthesia (group Ⅲ).Anesthesia was induced with iv midazolam,sufentanil,TCI of propofol and remifentanil and vecuronium in groups Ⅰ and Ⅲ.In group Ⅰ anesthesia was maintained with TCI of propofol and remifentanil and intermittent iv boluses of vecuronium,while in group Ⅲ with inhalation of sevoflurane and intermittent iv boluses of vecuronium.In group Ⅱ anesthesia was induced and maintained with inhalation of sevoflurane and intermittent iv boluses of vecuronium.Narcotrend index was used to monitor depth of anesthesia and maintained at 37-64 during operation.Venous blood samples were taken for determination of the levels of T lymphocyte subsets (CD3+,CD4+,CD8+,CD4+/CD8 +) and natural killer cells at 30 min before induction of anesthesia (T0),2 h after skin incision (T1),at the end of operation (T2) and 24 h after operation (T3).Results The levels of CD3 +,CD4 +,CD4+/CD8+ and natural killer cells were significantly decreased at T2 in group Ⅱ,while the levels of natural killer cells were decreased at T2 in group Ⅲ as compared with the baseline at T0,and were significantly lower than those in group Ⅰ.The levels of CD3+ and CD4+ were significantly lower at T2 in group Ⅱ than in group Ⅲ.Conclusion Intravenous anesthesia with midazolam,propofol,sufentanil,remifentanil and vecuronium has less inhibitory effect on perioperative cellular immune function than inhalational anesthesia and combined intravenous-inhalational anesthesia in patients undergoing laparoscopic surgery for colorectal cancer.