Objective To evaluate the effect of continuous transversus abdominis plane (TAP) block on postoperative systemic inflammatory responses of patients undergoing laparoscopic radical surgery for colorectal cancer. Methods Ninety-eight patients, aged 45-64 yr, of American Society of Anesthesiologists physical status Ⅱ or Ⅲ, weighing 50-75 kg, scheduled for elective laparoscopic radical surgery for colorectal cancer under general anesthesia, were divided into continuous patient-controlled epidural analgesia (PCEA) group (group PCEA) and continuous TAP block group (group TAPB) using a random number table, with 49 patients in each group.An epidural catheter was placed at L1, 2 interspace, a test dose of 3 ml of 2% lidocaine was given, and morphine 2 mg (in 10 ml of normal saline) was injected into the epidural space at the end of surgery in group PCEA.PCEA solution contained 0.15% ropivacaine and sufentanil 2 μg/ml (diluted to 300 ml in normal saline). PCA pump was set up with a 2 ml bolus dose, a 20 min lockout interval and background infusion at a rate of 4 ml/h.Catheterization of bilateral transversus abdominis plane was accomplished under ultrasound guidance, and 0.3% ropivacaine 20 ml was injected in group TAPB.TAP block solution contained 0.15% ropivacaine (diluted to 300 ml in normal saline). PCA pump was set up with a 6 ml bolus dose, a 30 min lockout interval and background infusion at a rate of 6 ml/h.Analgesia lasted until 48 h after surgery, and visual analogue scale score was maintained less than or equal to 3 in both groups.Parecoxib sodium 40 mg was intravenously injected as a rescue analgesic when visual analogue scale score was more than 3.Blood samples were collected from the right internal jugular vein at 24 h before operation (T0) and 48 h after operation (T1) for determination of the expression of CXCL8 mRNA in serum (by real-time polymerase chain reaction) and expression of CXCL8 and STAT3 in serum (by Western blot). The development of requirement for rescue analgesia, sensory motor dysfunction of lower extremities and nausea and vomiting after surgery was recorded. Results Compared with the baseline at T0, the expression of serum CXCL8 mRNA, CXCL8 and STAT3 was significantly up-regulated at T1 in the two groups (P 0.05). Conclusion Continuous TAP block can reduce postoperative systemic inflammatory responses of patients undergoing laparoscopic radical surgery for colorectal cancer. Key words: Nerve conduction block; Abdomen; Colon cancer; Rectal cancer; Inflammation