The basis for the transversus abdominis plane (TAP) block involves infiltration of a local anesthetic into the neurofascial plane between the internal oblique and the transversus abdominis muscles, causing a regional block that spreads between the L1 and T10 dermatomes. Thus, the TAP block is said to be suitable for lower abdominal surgery. This study was designed to compare the analgesic efficacy of two different concentrations of ropivacaine for TAP block in patients undergoing appendectomy.