Analgesic effect of transversus abdominis plane block (TAP block) in lower major abdominal laparoscopic surgery with about 5 cm of maximum surgical scar has been controversial. We hypothesized that TAP block has benefits, so the analgesic effect of TAP block after robot-assisted laparoscopic prostatectomy (RALP) was evaluated. One hundred patients were enrolled in this prospective, double-blinded, randomized study. Standardized general anesthesia with wound infiltration on camera port and fentanyl dose limit of 3 µg/kg was provided. Ultrasound-guided, singleshot subcostal TAP block with either 0.375% ropivacaine (Ropivacaine group, 48 patients) or normal saline (Control group, 52 patients) was performed by anesthesiologist in charge (34 anesthesiologists) after surgical procedure. Pain score using numerical rating scale (NRS) and postoperative intravenous fentanyl were evaluated for the first 24 postoperative hours. Median values (interquartile range) of NRS scores when the patients were transferred to post-anesthesia care unit (PACU) were 5 (2-7) in Ropivacaine group and 6 (4-8) in Control group at rest (P = 0.03), 5 (2-8) in Ropivacaine group and 7 (5-8) in Control group during movement (P < 0.01). These significant differences disappeared at the time of discharging PACU. Fentanyl doses for the first 24 postoperative hours were 210 µg (120-360) in Ropivacaine group and 200 µg (120-370) in Control group (P = 0.79). These results indicated that subcostal tAp block by anesthesiologists of varied level of training reduced postoperative pain immediate after RALP. TAP block had fundamental analgesic effect, but this benefit was too small to reduce postoperative 24-hour fentanyl consumption.In the past few decades, lower abdominal major surgical procedures such as colectomy, hysterectomy and prostatectomy have changed from laparotomy to laparoscopic methods. Although epidural anesthesia has been used as gold standard in laparotomy, smaller surgical scar in laparoscopic procedures and early recovery after surgery motivated us to consider peripheral nerve blocks instead of epidural anesthesia 1,2 .Transversus abdominis plane block (TAP block), first reported in 2001 3 , has recently been spreading as an alternative to epidural anesthesia. Analgesic effect of TAP block has been established in laparoscopic cholecystectomy 4-6 . Although enhanced recovery after surgery (ERAS) protocol in elective colorectal surgery recommended abdominal wall blocks because of postoperative less opioid use and early recovery2,decrease in pain score by TAP block in lower major abdominal laparoscopic procedures remains controversial 7-10 . One of reasons for this controversy is these major procedures require a larger port scar in order to extract resected organs. Furthermore, there are several technical biases affecting TAP block efficacy such as approach options, timing of TAP block (preoperative or postoperative), local anesthetic concentration and dose, and supplementary analgesics. It is necessary to minimize these biases when evaluating ...